Young boy brushing a baby's hair.
The baby is the boy's sibling
Just because a boy is brushing a baby's hair it does not mean it is his sibling.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & Theme(e1,x4) & Actor(e1,x2) & v_brush(e1) & n_hair(x4) & of(x4,x3) & n_baby(x3) & (x1 = x2) & n_boy(x1) & a_young(s1) & Theme(s1,x1))
exists p1 x1 x2 x3.(n_sibling(x3) & of(x3,x2) & n_boy(x2) & n_baby(x1) & (x1 = x3))