parent(nariman,zal).
parent(zal,sam).
parent(sam,rostam).
parent(sam,ghazanfar).
parent(sam,petros).
parent(rodabeh,sam).
parent(tahmineh,sohrab).
parent(rostam,sohrab).
parent(sodabeh,siyavash).
male(nariman).
male(zal).
male(sam).
male(rostam).
male(ghazanfar).
male(petros).
male(sohrab).
male(siyavash).
female(rodabeh).
female(tahmineh).
grand(X,Y) :- parent(X,Z),
	      parent(Z,Y).
grandmother(X,Y) :- grand(X,Y),
	            female(X).
grandfather(X,Y) :- grand(X,Y),
		    male(X).
grandfather(X,Y) :- parent(X,Z),
	            parent(Z,Y),
		    male(X).
grandparent(X,Y) :- grand(X,Z),
	            parent(Z,Y).

grandparent(X,Y) :- parent(X,Z1),
	            parent(Z1,Z2),
	            parent(Z2,Y).
spouse(X,Y) :- parent(X,Z),
	       parent(Y,Z),
	       X\=Y.