ASP Family

sibling(X,Y) :- parent(Z,X), parent(Z,Y).
mother(X,Y) :- parent(X,Y), female(X).
uncle(X,Y) :- parent(Z, Y), sibling(Z,X), male(X).
female(maria). male(mark). male(david).
parent(natalia, maria). parent(natalia, mark). parent(natalia, david).
parent(iakov, maria). parent(iakov, mark). parent(iakov, david).