male(peter).
male(john).
male(fred).
male(george).
male(alan).
male(bruno).

female(bruno).
female(mary).
female(lucy).
female(sandra).
female(jennifer).

parentOf(john,sandra,alan).
parentOf(mary,sandra,alan).
parentOf(lucy,jennifer,bruno).
parentOf(george,jennifer,bruno).
parentOf(peter,jennifer,bruno).
parentOf(alan,ladyX,alex).
parentOf(jennifer,ladyX,alex).

sibling(S1,S2):-parentOf(S1,Mo,Fa),parentOf(S2,Mo,Fa).

marriedTo(fred,lucy).
marriedTo(lucy,fred).
loves(george,mary).

ancestor(A,B):-parentOf(A,B,_).
ancestor(A,B):-parentOf(A,_,B).
ancestor(A,B):-parentOf(A,M,_),ancestor(M,B).
ancestor(A,B):-parentOf(A,_,F),ancestor(F,B).

related(A,B):-ancestor(A,X),ancestor(B,X).


likes(peter,mary).
likes(A,B):-loves(A,B).