% create parent relation ship
parent(adam, kain).
parent(eva, kain).
parent(adam, abel).
parent(eva, abel).
parent(adam, seth).
parent(eva, seth).
parent(sara, peter).
parent(abel, peter).
parent(sara, gunter).
parent(abel, gunter).
parent(seth, garfield).
parent(hela, garfield).

parent(bor, odin).
parent(odin, thor).
parent(odin, loki).

% create sex relation ship
male(adam).
male(peter).
male(gunter).
male(kain).
male(abel).
female(eva).
female(hela).
female(sara).

male(odin).
male(thor).
male(loki).
female(loki).

father(F,C):-parent(F,C),male(F).
mother(M,C):-parent(M,C),female(M).

grandparent(G, C):-parent(P,C),parent(G,P).
grandfather(G, C):-parent(P,C),parent(G,P),male(G).
grandmother(G, C):-parent(P,C),parent(G,P),female(G).

related(A,A).
related(A,B):-parent(A,B).
related(A,B):-parent(P,A),related(P,B).

% if A and B are siblings
siblings(A,B):-parent(P,A),parent(P,B).
% true if S is the a sister of A
sister(A,S):-siblings(A,S),female(S).
% true if B is the a brother of A
brother(A,B):-siblings(A,B),male(B).

aunt(A,B):-parent(P,B),sister(A,P).
uncle(A,B):-parent(P,B),brother(A,P).