Boy and girl running along the beach.
The boy and girl are siblings.
A boy and girl running doesn't mean they are siblings.
exists s1 x1 x2 x3 x4.(n_beach(x4) & ne_nam_boy(x1) & a_topic(s1) & subset_of(x2,s1) & along(x2,x4) & n_run(x2) & of(x2,x3) & n_girl(x3) & subset_of(x1,s1))
exists p1 x1 x2 x3.(n_girl(x3) & n_boy(x2) & subset_of(x3,x1) & subset_of(x2,x1) & exists x4.((x1 = x4) & n_sibling(x4)))