:- dynamic male/1, female/1, hasParentOf/2, spouse/2


hasxsggxsmotherOf(X,Y) :- parentOf(X,Y), female(X).

fatherOf(X,Y) :- parentOf(X,Y), male(X).

siblings(X,Y) :- parentOf(P1,X), parentOf(P1,Y), X \= Y.

isParent(X) :- parentOf(X,_).

childLess(X) :- \+ isParent(X).

grandparentOf(X, GP) :- parentOf(X, P), parentOf(P, GP).

