% Predicates for handling family relations ships.
% male, female, parent are taken as fundamental

father(X,Y):-parent(X,Y), male(X).
mother(X,Y):-parent(X,Y),female(X).
sister(X,Y):-parent(Z,X),parent(Z,Y),female(X),X\=Y.
brother(X,Y):-parent(Z,X),parent(Z,Y),male(X),X\=Y.
sibling(X,Y):-sister(X,Y).
sibling(X,Y):-brother(X,Y).
grandparent(X,Y):-parent(X,Z),parent(Z,Y).
grandfather(X,Y):-male(X),grandparent(X,Y).
grandmother(X,Y):-female(X),grandparent(X,Y).
grandchild(X,Y):-grandparent(Y,X).
child(X,Y):-parent(Y,X).
son(X,Y):-child(X,Y),male(X).
daughter(X,Y):-child(X,Y),female(X).
uncle(X,Y):-brother(X,P),parent(P,Y).
aunt(X,Y):-sister(X,P),parent(P,Y).
grandson(X,Y):-son(X,P),child(P,Y).
granddaughter(X,Y):-daughter(X,P),child(P).