Sibling: Difference between revisions

A '''sibling''' is a relative that shares at least one [[parent]] with the subjectother person. A [[male]] sibling is a [[brother]], and a [[female]] sibling is a [[sister]]. A personSomebody with no siblings is an [[only child]].

The word ''sibling'' was reintroduced in 1903 in an article in ''[[Biometrika]]'', as a translation for the German ''Geschwister'', having not been used since Middle English, specifically 1425.<ref>{{cite journal|year=1903|first1=Karl|last1=Pearson|author-link=Karl Pearson|first2=Alice|last2=Lee|author-link2=Alice Lee (mathematician)|journal=Biometrika|title=On the laws of inheritance in man|volume=2|issue=4|page=369|doi=10.2307/2331507|jstor=2331507|url=https://archive.org/details/blumenzeitung13hssl/page/369|quote=These [calculations] will enable us... to predict the probable character in any individual from a knowledge of one or more parents or brethren (“siblings,” = brothers or sisters).}}</ref><ref>{{cite web|url=https://getd.libs.uga.edu/pdfs/wang_elizabeth_g_200912_ma.pdf|title=Gone But Not Forgotten: Persistence and Revival in the History of English Word Loss|author=Elizabeth Grace Wang|pages=35–36|quote=The primary word under consideration in this chapter is sibling, which during the Old English period referred simply to a relation, not necessarily to a brother or sister, as in the modern use of the term. The last recorded use in the Oxford English Dictionary in the relative sense is in 1425. There are no records at all of the word for the next 500 years, although its derivational base sib remained in use throughout those years. It was in fact the term sib which, when employed specifically in the fields of anthropology and genetics, gave rise to the readoption of sibling. Sibling, in the narrower modern sense of describing the relationship between two people sharing a common parent, filled a semantic gap in the English lexicon, as there previously was no term to describe the fraternal relationship that did not specify gender. It is clear from early uses of sibling in the 20th century that the writer did not expect the reader to be familiar with the word, as the translator’s note from a German eugenics book, Human Heredity explains, ‘The word “sib” or “sibling” is coming into use in genetics in the English-speaking world, as an equivalent of the convenient German term “Geschwister” and as a general name for all children born of the same parents, that is to say, to denote brothers and sisters without distinction of sex.’ (Baur 1931: 508 in sibling, OED). Likewise, an article in the journal Biometrika from 1903 contains the clarification, ‘“siblings”=brothers or sisters,’ when employing the term. Thus we observe an interesting phenomenon of a native English word being reintroduced to native English speakers, who clearly have no knowledge of it.}}</ref>

{{anchor|Full}}Siblings or '''full -siblings''' ([''full''] ''sisters'' or ''brothers'') share the same biological parents. Full -siblings are also the most common type of siblings.{{Citation needed|date=June 2020}} [[Twin]]s are siblings that are born from the same pregnancy.<ref>{{Citation |title=twin |url=https://medical-dictionary.thefreedictionary.com/twin |work=The Free Dictionary |access-date=2023-06-22}}</ref> Often, twins with a close relationship will develop a [[twin language]] from infanthood, a language only shared and understood between the two. Studies suggestcorroborate that identical twins appear to display more twin talk than fraternal twins. At about 3 years of age, twin talk usually ends.<ref>{{cite journal|last1=Hayashi|first1=C|last2=Mikami|first2=H|last3=Nishihara|first3=R|last4=Maeda|first4=C|last5=Hayakawa|first5=K|title=The relationship between twin language, twins' close ties, and social competence|journal=Twin Research and Human Genetics |date=2014|volume=17|issue=1|pages=27–37|doi=10.1017/thg.2013.83|pmid=24330841|s2cid=31514697|doi-access=free}}</ref> Twins generally share a greater bond due to growing up together and being the same age.

{{anchor|Half}}'''Half-siblings''' ('''half-sisters''' or '''half-brothers''') are people who share one parent. They may share the same mother but different fathers (in which case they are known as ''uterine'' siblings or ''maternal half-siblings''), or they may have the same father but different mothers (in which case, they are known as ''agnate'' siblings or ''paternal half-siblings''. In law, the term ''[[Consanguinity|consanguine]]'' is used in place of agnate).{{citation needed|date=June 2020}} In law (and especially [[inheritance]] law), half-siblings have often been accorded treatment unequal to that of full -siblings. Old English [[common law]] at one time incorporated inequalities into the laws of [[Intestacy|intestate succession]], with half-siblings taking only half as much property of their intestate siblings' estates as siblings of full-blood. Unequal treatment of this type has been wholly abolished in [[England]],<ref>{{Cite web|title = Marriage: legitimacy and adoption|url = http://www.parliament.uk/about/living-heritage/transformingsociety/private-lives/relationships/overview/legitimacyadoption/|website = UK Parliament|access-date = 2015-08-03}}</ref> but still exists in the U.S. state of Florida.<ref>Fla. Stat. s. 732.105.</ref>

{{anchor|Three-quarter}}'''Three-quarter siblings''' share one parent, while the unshared parents are [[first-degree relativerelatives]]s to each other, for example, if a man has children with two women who are sisters, or a woman has children with a man and his son. In the first case, the children are half-siblings as well as first cousins; in the second, the children are half-siblings as well as an avuncular pair. They are genetically closer than half -siblings but less genetically close than full -siblings,<ref>{{Cite journal|last1=Graffelman|first1=Jan|last2=Galván Femenía|first2=Iván|last3=de Cid|first3=Rafael|last4=Barceló Vidal|first4=Carles|date=2019|title=A Log-Ratio Biplot Approach for Exploring Genetic Relatedness Based on Identity by State|journal=Frontiers in Genetics|language=English|volume=10|page=341|doi=10.3389/fgene.2019.00341|pmid=31068965|pmc=6491861|issn=1664-8021|doi-access=free}}</ref> a degree of genetic relationship that is rare in humans and little-studied.<ref>{{Cite journal|last1=Galván-Femenía|first1=Iván|last2=Barceló-Vidal|first2=Carles|last3=Sumoy|first3=Lauro|last4=Moreno|first4=Victor|last5=de Cid|first5=Rafael|last6=Graffelman|first6=Jan|date=15 January 2021|title=A likelihood ratio approach for identifying three-quarter siblings in genetic databases|journal=Heredity|language=en|volume=126|issue=3|pages=537–547|doi=10.1038/s41437-020-00392-8|pmid=33452467|pmc=8027836|issn=1365-2540|doi-access=free}}</ref>

===Non -blood relations{{anchor|step}}===<!--This section is linked from [[Barzan Ibrahim al-Tikriti]]-->

! Siblings and half -siblings

! Siblings, half -siblings, and three-quarter siblings

|style="font-size:94%; border: none; line-height: 1.4em; max-width: 100px;" |Erika and Efram are full siblings; Toto them, Abram, Aserna, and Agnia are their half -siblings, and Bein is their cross sibling.<br>Julia and Janine were born to one father and two full-sibling mothers, and are thus three-quarter siblings. Jaden is their cousin, while Jrake and Jakob are their half-cousins.<br>Jrake and Jaden were born to one mother and two half-sibling fathers, and are thus three-quarter siblings, however, their actual percentage of genetic relation is 31.25% instead of 37.5%. Jrake and Jakob are cross -cousins.

[[Consanguinity]] is the measure of how closely people are related.<ref>{{Cite web|last=nivens|date=2015-01-09|title=Consanguinity|url=https://adoption.umn.edu/consanguinity|access-date=2021-03-02|website=Adoption Medicine Clinic – University of Minnesota|language=en|archive-date=2021-03-05|archive-url=https://web.archive.org/web/20210305135928/https://adoption.umn.edu/consanguinity|url-status=dead}}</ref> Genetic relatedness measures how many genes a person shares. As all humans share over 99% of the same genes, consanguinity only matters for the small fraction of genes which vary between different personspeople.<ref name="Understanding genetics">{{cite web|last=Dr. Shafer|first=Aaron|title=Understanding genetics|url=http://genetics.thetech.org/ask/ask166|website=The Tech|publisher=Stanford University|access-date=13 December 2013}}</ref> Inheritance of genes has a random element to it,<ref name="Understanding genetics"/> and these two concepts are different.<ref name="Why half siblings share 25% of their DNA - Understanding">{{cite web|last=Dr. Starr|first=Barry|title=Why half siblings share 25% of their DNA – Understanding|url=http://genetics.thetech.org/ask-a-geneticist/why-siblings-share-around-fifty-percent-their-dna|website=The Tech|date=5 September 2013 |publisher=Stanford University|access-date=19 June 2014}}</ref> Consanguinity decreases by half for every generation of reproductive separation through their most recent common ancestor. Siblings are 50% related by consanguinity as they are separated from each other by two generation (sibling to parent to sibling), and they share two parents as common ancestors (<math>\left ( \tfrac{1}{2} \right )^2 + \left ( \tfrac{1}{2} \right )^2</math>).

A fraternal twin is a sibling and, therefore, is related by 50% consanguinity.<ref>{{Cite web|title=Coefficient of relationship – ISOGG Wiki|url=https://isogg.org/wiki/Coefficient_of_relationship|access-date=2021-03-02|website=isogg.org}}</ref> [[Fraternal twins]] are no more genetically similar than regular siblings. As [[identical twin]]s come from the same zygote, their most recent common ancestor is each other. They areThey’re genetically identical and 100% consanguineous as they arethey’re separated by zero generations (<math>\left ( \tfrac{1}{2} \right )^0</math>).<ref name="Understanding genetics"/> [[Twin study|Twin studies]] have been conducted by scientists to examine the roles that [[Nature versus nurture|genetics and environment]] play in the development of various traits. Such studies examine how often identical twins possess the same behavioral trait and compare it to how often fraternal twins possess the same trait.{{citation needed|date=June 2020}} In other studies twins are raised in separate families, and studies compare the passing on of a behavioral trait by the family environment and the possession of a common trait between identical twins. This kind of study has revealed that for personality traits which are known to be [[Heritability|heritable]], genetics play a substantial role throughout life and an even larger role during early years.<ref>{{cite journal|last1=Plomin|first1=R|last2=Pederson|first2=N.L.|last3=McClearn|first3=G.E.|last4=Nesselroade|first4=J.R.|last5=Bergeman|first5=C.S.|title=EAS temperaments during the last half of the life span: Twins reared apart and twins reared together|journal=Psychology and Aging|date=1988|volume=3|issue=1|pages=43–50|doi=10.1037/0882-7974.3.1.43|pmid=3268242}}</ref>

Half -siblings are 25% related by consanguinity as they share one parent and separated from each other by two generations (<math>\left ( \tfrac{1}{2} \right )^2</math>).

A person may share more than the standard consanguinity with their sibling if their parents are related (the [[coefficient of inbreeding]] is greater than zero).{{citation needed|date=June 2020}} {{anchor|3quarters}}Interestingly, half -siblings can be related by as "three -quarters siblings" (related by 3/8) if their unshared parents have a consanguinity of 50%. This means the unshared parents are either siblings, making the half -siblings [[cousin]]s, or parent and child, making them half- [[aunt]]-[[uncle]] and [[niece]]-[[nephew]].<ref>{{cite web |url=https://genetics.thetech.org/ask/ask430 |title=Understanding Genetics |website=genetics.thetech.org|date=22 January 2022 }}</ref>

In practice, full siblings do not share exactly 50% of their DNA, as [[chromosomal crossover]] only occurs a limited number of times and, therefore, large chunks of a chromosome are shared or not shared at one time. In fact, the mean DNA fraction shared is 50.28% with a standard deviation of 3.68%,<ref>{{cite journal | pmc=4037293 | year=2013 | last1=Vinkhuyzen | first1=A. A. | last2=Wray | first2=N. R. | last3=Yang | first3=J. | last4=Goddard | first4=M. E. | last5=Visscher | first5=P. M. | title=Estimation and Partitioning of Heritability in Human Populations using Whole Genome Analysis Methods | journal=Annual Review of Genetics | volume=47 | pages=75–95 | doi=10.1146/annurev-genet-111212-133258 | pmid=23988118 }}</ref> meaning approximately 1/4 of sibling pairs share more than 52.76% of their DNA, while 1/4 share less than 47.8%.<ref>Calculated based on the [[Standard deviation#Rules for normally distributed data|normal distribution]]</ref>

There is a very small chance that two half-siblings might not share any genes, if they didn't inherit any of the same chromosomes from their shared parent. This is possible for full -siblings as well, though even more unlikely. But because of how [[homologous chromosomes]] swap genes (due to [[chromosomal crossover]] during [[meiosis]]) during the development of an egg or sperm cell, however, the odds of this ever actually occurring are practically non-existent.<ref name="Why half siblings share 25% of their DNA - Understanding"/>

Birth order is a person's rank by age among his or her siblings. Typically, researchers classify siblings as "eldest", "middle child", and "youngest" or simply distinguish between "firstbornfirst-born" and "later-born" children.

Birth order is commonly believed in [[pop psychology]] and popular culture to have a profound and lasting effect on psychological development and [[Personality psychology|personality]]. For example, firstborns are seen as conservative and high -achieving, middle children as natural mediators, and youngest children as charming and outgoing. Despite its lasting presence in the public domain, studies have failed to consistently produce clear, valid, and compelling findings.; Thereforetherefore, it has earned the title of a [[Pseudoscience|pseudo-psychology]] amongst the scientific psychological community.<ref name="Psychology Around Us">{{cite book|last1=Comer|first1=Ronald|last2=Gould|first2=Elizabeth|last3=Ogden|first3=Nancy|last4=Boyes|first4=Michael|title=Psychology Around Us|url=https://archive.org/details/psychologyaround0000come|url-access=registration|date=February 2012|publisher=Wiley}}</ref>

[[File:Sir Joshua Reynolds 004- Lady Cockburn and Her Three Eldest Sons (1773-1775).jpg|thumb|''[[Portrait of Lady Cockburn and her Three Eldest Sons]]'' (1773–1775) by [[Joshua Reynolds]]]]