* wife(x,y) means "the wife of x is y."

s all x all y wife(x,y) then spouse(x,y) & female(y);
s all x all y husband(x,y) then spouse(x,y) & male(y);
s all x all y son(x,y) then child(x,y) & male(y);
s all x all y daughter(x,y) then child(x,y) & female(y);
s all x all y brother(x,y) then sibling(x,y) & male(y);
s all x all y sister(x,y) then sibling(x,y) & female(y);
s all x all y mother(x,y) then parent(x,y) & female(y);
s all x all y father(x,y) then parent(x,y) & male(y);

s all x male(x) xor female(x);
s all x all y child(y,x) then parent(x,y) ;
s all x all y husband(x,y) then wife(y,x);
s all x all y sibling(x,y) then sibling(y,x);
s all x all y all z parent(y,x) & child(x,z) & male(z) then brother(y,z);
s all x all y all z parent(y,x) & child(x,z) & female(z) then sister(y,z);
* all x all y all z parent(y,x) & sibling(y,z) & male(z) then son(x,z);
* all x all y all z parent(y,x) & sibling(y,z) & female(z) then daughter(x,z);

eof