predicates
	nondeterm grandparent(symbol, symbol).		
	nondeterm parent(symbol, symbol).
	nondeterm kid(symbol, symbol).
	nondeterm sibling(symbol, symbol).
clauses
	/*Dad's branch*/
	parent("Sergey","Evgenij").
	parent("Tatyana","Evgenij").
	parent("Evgenij","Kirill").
	parent("Evgenij","Bonya").
	/*Mom's branch*/
	parent("Vladimir","Oksana").
	parent("Nina","Oksana").
	parent("Oksana","Kirill").
	parent("Oksana","Bonya").
	/**/
	sibling(F,S):-parent(M,F) and parent(D,F) and parent(M,S) and parent(D,F).
	kid(C,P):-parent(P,C).
	grandparent(GP,C):-parent(GP,P) and parent(P,C).
goal
	grandparent("Vladimir", "Kirill").