The on-sale date is from the publication date recorded in the Catalog of Copyright Entries, Third Series, Part 2, Periodicals, 1946-1947.
1st Marvel Family story, but the Marvel Family first appears in Captain Marvel Adventures #18, which retells the origins of Captain Marvel, Captain Marvel, Jr., and Mary Marvel.
Inker credit, verified by Marc Swayze, revised from C.C. Beck to Costanza by Craig Delich 2012-7-15.
Baby Marvel was a Marvel in name only and made only one appearance.