uncle(Uncle,Person) :-
	brother(Uncle,Parent), parent(Parent,Person).

sibling(Sib1,Sib2) :-
	parent(Parent,Sib1), parent(Parent,SIb2), Sib1 \= Sib2.

cousin(Cousin1,Cousin2) :-
	parent(Parent1,Cousin1),
	parent(Parent2,Cousin2),
	sibling(Parent1,Parent2).

%Program 2.1:  Defining family relationships