		/* Family Relationships */

f(Bob) => Gary.
m(Bob) => Mary.
f(Ann) => Gary.
m(Ann) => Mary.
f(Gary) => Joe.
m(Gary) => Jane.
f(Mary) => Steve.
m(Mary) => Sue.
f(Joe) => Dan.
m(Joe) => Donna.
m(Jane) => Diane.
m(Steve) => Diane.

p(x) => f(x).
p(x) => m(x).
gp(x) => p(p(x)).

sib(x) => y where z <- p(x);  z = p(y); eq(x,y) = false. 

cous(x) => y where p(x) = sib(p(y)).
		  
anc(x) => p(x).
anc(x) => anc(p(x)).
