Logic

The following program says that two people are relatives if

one is a predecessor of the other, or

they have a common predecessor, o r

they have a common successor.

relatives(X,Y) :- predecessor( X,Y).

relatives(X,Y) :- predecessor(Y,X).

relatives(X,Y) :- predecessor(Z,X), predecessor(Z,Y).

relatives(X,Y) :- predecessor(X,Z), predecessor(Y,Z).

Can you shorten this program by using the combination of coma and semicolon notation?