Solution

father_of(X,Y) :- male(X),
parent_of(X,Y).

mother_of(X,Y) :- female(X),
parent_of(X,Y).

grandfather_of(X,Y) :- father_of(X,Z),
parent(Z,Y).

grandmother_of(X,Y) :- mother_of(X,Z),
parent(Z,Y).

sister_of(X,Y) :- female(X),
parent_of(Z,X),
parent_of(Z,Y).

brother_of(X,Y) :- male(X),
parent_of(Z,X),
parent_of(Z,Y).

aunt_of(X,Y) :- sister_of(X,Z),
parent_of(Z,Y).

uncle_of(X,Y) :- brother_of(X,Z),
parent_of(Z,Y).

Last modified: Wed Dec 1 13:26:37 CET 2004