Before the house was swept away by cyclone little Dorothy “lived in the midst of the great Kansas prairies, with Uncle Henry, who was a farmer, and Aunt Em, who was the farmer's wife.” That’s the way L. Frank Baum puts it in the opening sentence of The Wonderful Wizard of Oz. The order in which they’re introduced suggests that Uncle Henry is Dorothy’s blood relation, with his wife Dorothy’s aunt by marriage. In a sequel to Wizard Baum gives Dorothy’s last name as Gale. He never (so far as I recall) explicitly says whether Henry’s last name is Gale, too.
At the Oz convention this summer I asked a couple friends and Oz scholars if they knew of any post-Baum Oz historian who had given Dorothy parents. Eric Gjovaag remembered an author who had written about Dorothy as though she were a real person and this author had suggested Dorothy was not biologically related either to her “Uncle” or to her “Aunt” but had been shipped West on an orphan train. I thought that an interesting take. I didn’t write any of this down so I’ve forgotten the author and title. I’ll write Eric and see if he remembers.
Anyway, I am reading volume one of The Complete Annotated Oz Squad by Steve Ahlquist and see that he has given Uncle Henry a last name different from Dorothy’s. A panel of the comic shows a mailbox. Explains Ahlquist, “The name on the mailbox is Snow, Dorothy’s mother’s maiden name. Uncle Henry is Dorothy’s mother’s brother.”
In volume two we learn that Henry’s sister is a prominent person in Oz who has been of much help to her daughter.