How to define a relative rule in Prolog?

Question

How to define a relative rule in Prolog?

This is what I got so far:

spouce(X,Y) :-
    wife(X,Y).

spouce(X,Y) :-
    husband(X,Y).

relative-by-blood(X,Y) :-
    ancestor(Z,X),
    ancestor(Z,Y).


relative(X,Y) :-
    relative-by-blood(X,Y).

relative(X,Y) :-
    spouce(X,Y).

relative(X,Y) :-
    relative-by-blood(X,Z), %<- not sure what to do here.

Thanks in advance!

Answer 1

Well, for starters, I think you need to rewrite relative(X,Y) as:

relative(X,Y) :- relative-by-blood(X,Y) ; spouce(X,Y).

From there we need more info (I'll edit to add to my answer if we get more). Also, can you give us your ancestor rules?