a little girl pushes a little boy on the swing.
The little girl and boy are siblings.
girl  doesn't always mean  siblings.
exists e1 s1 s2 x1 x2 x3.(n_swing(x3) & Theme(e1,x2) & Actor(e1,x1) & v_push(e1) & on(x2,x3) & n_boy(x2) & a_little(s2) & Theme(s2,x2) & n_girl(x1) & a_little(s1) & Theme(s1,x1))
exists p1 s1 x1 x2 x3.(n_boy(x3) & n_girl(x2) & subset_of(x3,x1) & subset_of(x2,x1) & a_little(s1) & Theme(s1,x1) & exists x4.((x1 = x4) & n_sibling(x4)))