sibling(X, Y) :- mother(M, X), mother(M, Y), father(F, X), father(F, Y), not(X=Y).
mother(X, Y) :- parent(X, Y), female(X).
father(X, Y) :- parent(X, Y), male(X).
brother(X, Y) :- sibling(X, Y), male(X).
sister(X, Y) :- sibling(X, Y), female(X).

grandparent(X, Y) :- parent(X, Y).
husband(X, Y) :- married(X, Y), male(X).
wife(X, Y) :- married(X, Y), female(X).
child(X, Y) :- parent(X, Y).

female(artemis).
female(hebe).
female(hera).
female(hestia).
female(rhea).
female(leto).
male(apollo).
male(ares).
male(cronus).
male(hades).
male(hephaestus).
male(poseidon).
male(zeus).

married(cronus, rhea).
married(zeus, hera).
married(zeus, leto).
married(poseidon, amphitrite).
married(hades, persephone).

parent(cronus, zeus).
parent(rhea, zeus).
parent(cronus, poseidon).
parent(rhea, poseidon).
parent(cronus, hades).
parent(rhea, hades).
parent(cronus, hestia).
parent(rhea, hestia).
parent(zeus, ares).
parent(hera, ares).
parent(zeus, hebe).
parent(hera, hebe).
parent(zeus, hephaestus).
parent(hera, hephaestus).
parent(zeus, apollo).
parent(leto, apollo).
parent(zeus, artemis).
parent(leto, artemis).