Two young boys playing on the rocks.
They are brothers.
Not all young boys playing on rocks together are brothers.
exists e1 s1 x1 x2 x3.(n_rock(x3) & a_topic(x1) & on(e1,x3) & Actor(e1,x2) & v_play(e1) & (x1 = x2) & n_boy(x1) & a_young(s1) & Theme(s1,x1) & card_eq_2(x1))
exists p1 x1.(n_thing(x1) & exists x2.((x1 = x2) & n_brother(x2)))