grandchild(X, Z) :- child(X, Y), child(Y, Z).
 
child(hideyasu, ieyasu).
child(hidetada, ieyasu).
child(yoshinao, ieyasu).
child(yorinobu, ieyasu).
child(yorifusa, ieyasu).
 
child(iemitsu, hidetada).
child(tadanaga, hidetada).
child(masayuki, hidetada).
 
child(ietsuna, iemitsu).
child(tsunayoshi, iemitsu).
 
program :- 
	findall(X, grandchild(X, ieyasu), Bag),
	print(Bag).