Выводит не все строчки ответа (Turbo Prolog)

Формулировка задачи:

predicates
 parents(String, String)
 man(String)
 woman(String)
 sister(String, String)
 brother(String, String)
 father(String, String)
 mother(String, String)
 grandfather(String, String)
 grandmother(String, String)
 print
clauses
  parents("Tom","Ellen"). 
  parents("Tom", "Chris").
  parents("Jane", "Ellen").
  parents("Jane", "Chris").
  parents("John", "Jane").
  parents("Eve","Tom").
 man("Tom").
 man("Chris").
 man("John").
 woman("Ellen").
 woman("Jane").
 woman("Eve").

 sister(X, Y) :- parents(Z, X), parents(Z, Y), woman(X), X<>Y.

 brother(X, Y) :- parents(Z, X), parents(Z, Y), man(X), X<>Y.

 father(X, Y) :- parents(X, Y), man(X), X<>Y.

 mother(X, Y) :- parents(X, Y), woman(X), X<>Y.

 grandfather(X, Y) :- parents(X,Z), parents(Z, Y), man(X), X<>Y.

grandmother(X, Y) :- parents(X,Z), parents(Z, Y), woman(X), X<>Y.
print:-sister(X,Y), write(X,"- sister -", Y), nl, fail.
print:-brother(X,Y), write(X,"- brother -", Y), nl, fail.
 print:-father(X,Y), write(X,"- father -", Y), nl, fail.
 print:-mother(X,Y), write(X,"- mother -", Y), nl, fail.
print:-grandfather(X,Y), write(X,"- grandfather -", Y), nl, fail.
print:-grandmother(X,Y), write(X,"- grandmother -", Y), nl, fail.
print.
GOAL
    print,
    readln(I).

Программа выводит ответ начиная с второго print. Как исправить?

Решение задачи: «Выводит не все строчки ответа (Turbo Prolog)»

textual
                            Листинг программы 
                        

                            sister(X, Y):- woman(X), parents(Z, X), parents(Z, Y).
 
brother(X, Y):- man(X), parents(Z, X), parents(Z, Y).
  
father(X, Y):- man(X),parents(X, Y).
 
mother(X, Y):- woman(X), parents(X, Y). 
  
grandfather(X, Y):- man(X), parents(X,Z), parents(Z, Y).
 
grandmother(X, Y):- woman(X), parents(X,Z), parents(Z, Y).
print:-sister(X,Y), write(X),write('- sister -'), write(Y), nl, fail.
print:-brother(X,Y), write(X),write('- brother -'), write(Y), nl, fail.
print:-father(X,Y), write(X),write('- father -'), write(Y), nl, fail.
print:-mother(X,Y), write(X),write('- mother -'), write(Y), nl, fail.
print:-grandfather(X,Y), write(X),write('- grandfather -'), write(Y), nl, fail.
print:-grandmother(X,Y), write(X),write('- grandmother -'), write(Y), nl, fail.
print.
 
parents('Tom','Ellen'). 
parents('Tom', 'Chris').
parents('Jane', 'Ellen').
parents('Jane', 'Chris').
parents('John', 'Jane').
parents('Eve','Tom').
 man('Tom').
 man('Chris').
 man('John').
 woman('Ellen').
 woman('Jane').
 woman('Eve').
                        