I have to think the father of this family is permanently out getting dinner; from what I can find with a little research, this set only ever included these three! I can't find a definite date, but they feel 1940s or so to me. I personally love that there is some wear to the paint on their heads, especially on the babies, one assumes from knocking around inside their mother! I'd free them and keep them lined up as a happy family.
Large one measures 3 1/8" t x 1 1/2" in diameter. Some wear around the edges and on her right flipper, as well as on the top of the heads as mentioned. No notable warping; the large one opens with ease and tightly closes.