A search for the founder member(s) responsible for the familial hypercholesterolaemia (FH) gene(s) in the RSA inadvertently revealed the existence of a marriage which links two pedigrees in which FH occurs. This marriage could result in the birth of an FH homozygote child. The couple concerned should have--but had not--been informed of the implications of their union before their marriage. The importance of identifying individuals at risk through extensive tracing of families in which FH occurs and the relevance of subsequent counselling are illustrated.