%

% Facts about our family tree

%

parent(chester,irvin).

parent(chester,clarence).

parent(chester,mildred).

parent(irvin,ron).

parent(irvin,ken).

parent(clarence,shirley).

parent(clarence,sharon).

parent(clarence,charlie).

parent(mildred,mary).

%

% More facts

%

male(chester).

female(mildred).

male(irvin).

female(shirley).

male(clarence).

female(sharon).

male(ron).

female(mary).

male(ken).

male(charlie).

%

% associations

%

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

mother(X,Y) :- parent(X,Y), female(X).

grandparent(X,Y) :- parent(X,Z), parent(Z,Y).

paternalgrandfather(X,Y) :- father(X,Z), father(Z,Y).

sibling(X,Y) :- parent(Z,X), parent(Z,Y).

brothers(X,Y) :- sibling(X,Y),male(X),male(Y), \+ (X=Y).