parent(john,donna).
parent(john,george).
parent(john,mary).
parent(catherine,donna).
parent(catherine,george).
parent(catherine,mary).
parent(pamela,james).
parent(george,james).
parent(mary,julia).
parent(mary,peter).
parent(richard,julia).
parent(richard,peter).
parent(peter,melissa).
parent(harriet,melissa).
parent(henry,harriet).
parent(henry,susan).
parent(roberta,harriet).
parent(roberta,susan).
parent(robert,stephen).
parent(robert,henry).
parent(elizabeth,stephen).
parent(elizabeth,henry).
female(donna).
female(mary).
female(elizabeth).
female(roberta).
female(caterine).
female(pamela).
female(harriet).
female(julia).
female(susan).
female(melissa).
male(george).
male(john).
male(richard).
male(peter).
male(james).
male(henry).
male(stephen).
male(robert).
married(john,catcherine).
married(george,pamela).
married(richard,mary).
married(peter,harriet).
married(henry,roberta).
married(robert,elizabeth).
brother(X,Y):-male(X),parent(Z,X),parent(Z,Y).
sibling(X,Y):-parent(Z,X),parent(Z,Y),X\==Y.
cousin(X,Y):-parent(W,X),parent(Z,Y),sibling(W,Z).
grandparent(X,Y):-parent(X,Z),parent(Z,Y).
void(X,Y):-married(X,Z),Y\==Z.