Two boys rollerblading.
The boys are brothers.
Not all boys are brothers.
exists e1 x1.(Actor(e1,x1) & v_rollerblade(e1) & n_boy(x1) & card_eq_2(x1))
exists p1 x1.(n_boy(x1) & exists x2.((x1 = x2) & n_brother(x2)))