The young couple share a humorous joke while traveling on the coach bus.
The couple are in a relationship with each other.
The young couple is a couple and they being sharing a humorous joke while traveling on the coach bus means in a relationship with each other.
(x)
exists p1 x1.(n_couple(x1) & exists x2.(all x3.(n_other(x3) -> (in(x1,x2) & with(x2,x3))) & n_relationship(x2)))