male(joe).
male(fred).
male(fred).
male(phil).
male(tom).
male(larry).
male(john).
male(george).
male(mike).
male(chuck).
male(hal).
male(harry).
male(wally).
female(jane).
female(mary).
female(jill).
female(chris).
female(alice).
female(jenny).
female(ann).
female(dianne).
female(debbie).
female(marge).
female(patty).
parent(joe,mary).
parent(jane,mary).
parent(joe,phil).
parent(jane,phil).
parent(joe,tom).
parent(jane,tom).
parent(joe,alice).
parent(jane,alice).
parent(mary,john).
parent(fred,john).
parent(mary,george).
parent(fred,george).
parent(tom,ann).
parent(jill,ann).
parent(tom,dianne).
parent(chris,dianne).
parent(alice,hal).
parent(larry,hal).
parent(alice,harry).
parent(larry,harry).
parent(dianne,debbie).
parent(mike,debbie).
parent(jenny,chuck).
parent(john,chuck).
parent(hal,patty).
parent(marge,patty).
parent(chuck,wally).
parent(patty,wally).

father(X,Y) :- parent(X,Y), male(X).
mother(X,Y) :- parent(X,Y), female(X).
grandparent(X,Y) :- parent(X,Z), parent(Z,Y).
ancestor(X,Y) :- parent(X,Y).
ancestor(X,Y) :- parent(X,Z), ancestor(Z,Y). 
siblings(A,B) :- parent(Z,A), parent(Z,B), not(A=B).