A man and two children in life jackets in a boat on a lake.
A father and sons are fishing on the lake.
A man and two children aren't necessarily father and sons, and you can be on a boat without actually fishing.
exists x1 x2 x3 x4 x5 x6.(a_topic(x1) & in(x1,x3) & in(x3,x5) & on(x5,x6) & n_lake(x6) & n_boat(x5) & n_jacket(x3) & of(x3,x4) & n_life(x4) & n_child(x1) & card_eq_2(x1) & of(x1,x2) & n_man(x2))
exists e1 x1 x2 x3 x4.(n_lake(x4) & on(e1,x4) & Actor(e1,x1) & v_fish(e1) & n_son(x3) & n_father(x2) & subset_of(x3,x1) & subset_of(x2,x1))