%trace
predicates
    
    father(symbol,symbol)
    mother(symbol,symbol)
    male(symbol)
    female(symbol)
%    uncle(symbol,symbol)
    husband(symbol,symbol)
    
    sister(symbol,symbol)
    brother(symbol,symbol)
    grandfather(symbol,symbol)
    grandmother(symbol,symbol)
    aunty(symbol,symbol)
    
clauses

    father(satishbhai,dhirajlal).
    father(bharatbhai,dhirajlal).
    father(hemal,satishbhai).
    father(neha,satishbhai).
    father(nirav,bharatbhai).
    father(bhavanaben,kantilal).
    father(gitaben,keshavbhai).
    
    mother(hemal,bhavanaben).
    mother(neha,bhavanaben).
    mother(bhavanaben,vasumatiben).
    mother(nirav,gitaben).
    mother(pintu,gitaben).
    mother(gitaben,sharadaben).
    mother(satishbhai,sharadaben).
    mother(bharatbhai,sharadaben).
    
    male(hemal).
    male(nirav).
    male(satishbhai).
    male(bharatbhai).
    male(dhirajlal).
    male(kantilal).
    male(keshavbhai).
    
    female(neha).
    female(pintu).
    female(bhavanaben).
    female(bijal).
    female(gitaben).
    female(vasumatiben).
    female(sharadaben).

    husband(bhavanaben,satishbhai).
    husband(gitaben,bharatbhai).
    husband(bijal,nirav).

    uncle(hemal,bharatbhai).
    uncle(nirav,satishbhai).
    
    brother(X,Y) :- father(X,A),father(Y,A),male(X),male(Y).
%    brother(X,Y) :- brother(Y,X),male(X),male(Y).
    
    sister(X,Y) :- father(X,A),father(Y,A),female(Y).
    
    aunty(X,Y) :- husband(Y,Z),
              brother(Z,W),
              Z <> W,
              father(X,W).

    grandfather(X,Y) :-
        male(Y), 
        father(X,W),
        father(W,Y).

    grandfather(X,Y) :-
        male(Y),
        mother(X,W),
        father(W,Y).

    grandmother(X,Y) :-
        female(Y), 
        father(X,W),
        mother(W,Y).

    grandmother(X,Y) :-
        female(Y),
        mother(X,W),
        mother(W,Y).