first_cousin_twice_removed(C1, C2) :-

parent(Y,X) :- child(X,Y).

father(Y,X) :- child(X,Y), male(Y).

grand_father(X,Z) :- father(X,Y), parent(Y,Z).
mother(M,C):- child(C,M),female(M).

grand_parent(GP,GC):- parent(GP,P), parent(P,GC).

grand_mother(GM,GC):- grand_parent(GM,GC), female(GM).

great_grand_parent(GGP,GGC):- parent(P,GGC), grand_parent(GGP,P).

great_grand_mother(GGM,GGC):- grand_parent(Z,GGC), parent(GGM,Z), female(GGM).

first_cousin(C1,C2):- parent(P1,C1), parent(P2,C2), sibling(P1,P2).

second_cousin(X,Y):- great_grand_parent(Z,X), great_grand_parent(Z,Y), +sibling(X,Y),+cousin(X,Y), X=Y.

half_first_cousin(C1,C2):- parent(P1,C1), parent(P2,C2),half_sibling(P1,P2), C1=C2.

double_first_cousin(C1,C2):- parent(P1,C1), parent(P2,C1), parent(P3,C2), parent(P4,C2), sibling(P1,P3), sibling(P2,P4), C1=C2, P1=P2, P3=P4.