A mom and son having fun at the lake during winter.`
The mom and son are a family.
Mom and son are part of same family who are having fun at the lake.
(x)
exists p1 x1 x2 x3.(n_son(x3) & n_mom(x2) & subset_of(x3,x1) & subset_of(x2,x1) & exists x4.((x1 = x4) & n_family(x4)))