A person's birth (including the relationship of birth father and birth mother to child) is typically modeled like this:
<#birth>
rdf:type gc:Birth ;
gc:hasPlayer <#player1> ;
gc:hasPlayer <#player2> ;
gc:hasPlayer <#player3> .
<#player1>
rdf:type gc:BirthFather ;
gc:playedBy <#person1> .
<#player2>
rdf:type gc:BirthMother ;
gc:playedBy <#person2> .
<#player3>
rdf:type gc:Child ;
gc:playedBy <#person3> .
Where the sex of a parent is indeterminate, the player type gc:BirthParent (which is the superclass of gc:BirthFather and gc:BirthMother) can be specified instead.
You can use a birth event to refer to an individual's birth even when the details are unknown. This is useful, for example, when the event is used as the basis of some other interval (such as a maiden name, which is had as the actual name from birth until marriage).