I've got to dash right now so I don't have time to check it, but as I recall, Maybelle was a cousin of Sara's, but she was married to Ezra Carter, A. P.'s brother. The girls (June, et al) are the daughters of Ezra and Maybelle.

I think that's it. If no one beats me to it, I'll check the aforementioned book and try to get back to you tomorrow.

Don Firth