/* this is our first program */

 

% a second comment

 

parent(john, peter).

parent(mary, peter).

parent(john, andrew).

parent(mary,andrew).

 

 

father(Father,Child) :-

                        male(Father),

                        parent(Father,Child).

 

mother(Mother,Child) :- female(Mother),

                        parent(Mother,Child).

 

 

male(john).

male(peter).

male(andrew).

 

female(mary).

female(kate).

 

 

brother(Brother1,Brother2) :-

             male(Brother1),

             male(Brother2),

             father(Parent1,Brother1),

             father(Parent1,Brother2),

             mother(Parent2,Brother1),

             mother(Parent2,Brother2),

             not(Brother1 = Brother2).