Moselle Graycomb (neé Stemple) was the daughter of Riva Herrin and Paco Stemple. Her siblings were Louise and Jacques. She married Amos Graycomb, her second cousin, and they had four children: Zita, Howie, Betty and Olivia.
She was a second cousin of "Old Tut" Simpson, Homer Simpson's great-grandfather, but if the story of Virgil being the ancestor of the Simpson family told by Abe is true, then Moselle would no longer be related to them, and would be instead related to Hiram and Eliza Simpson, who are ancestors of the Van Houten family.