Tom Blackett was a 3-year-old brother to the Amazons, at one time considered by Arthur Ransome as a character in Swallows and Amazons. The little chap did not survive the rewriting of the book before publication. A draft list of the characters including Blackett family children was on p31 and 32 of Roger Wardale's book "in search of Swallows & Amazons" (and in CFT p22):
Amazons: Jane 13, Mary (proper name Ruth) 12, Tom 3.
Parents to Amazons: Smith (scored out) Walker.
Amazons: Jane (scored out) Nancy 13, Mary (scored out) Peggy 12, Tom 3.