Young men often define themselves and their masculine identity through romantic and sexual relationships, and their resulting sexual decisions can affect their successful transition into adulthood, as well as STI, HIV and pregnancy rates. This paper looks at how young Paraguayan men's peer groups, family and masculine identity formation influence their behaviours in sexual and romantic relationships. In Asunción, Paraguay, we conducted five focus-group discussions (FGDs) examining neighbourhood norms in 2010, with male peer groups ranging in age from 14 to 19 years. We then interviewed half the members from each peer group to examine their relationships with friends, family and young women and their beliefs about existing gender norms. Young men described two types of masculine norms, 'partner/provider' and macho, and two types of romantic relationships, 'casual' and 'formal'. The language used to describe each spectrum of behaviours was often concordant and highlights the connection between masculine norms and romantic relationships. The perceived norms for the neighbourhood were more macho than the young men's reported behaviours. Norms cannot change unless young men speak out about their non-normative behaviours. This provides evidence for more research on the formation, meaning and transformation of male gender norms.