@prefix : <http://example.org/> .

:noChildrenOk a :Person .
:oneMaleChildOk a :Person ; :child [ :gender "male" ] .
:twoMaleChildrenOk a :Person ; :child [ :gender "male" ], [ :gender "male" ] .
:oneFemaleChildNotOk a :Person ; :child [ :gender "female" ] .
:mixedChildrenNotOk a :Person ; :child [ :gender "male" ], [ :gender "female" ] .
:twoFemaleChildrenNotOk a :Person ; :child [ :gender "female" ], [ :gender "female" ] .