Hi
Llanystumdwy does not appear to be included.
Family tree is in Achau ...... by T.Ceiri Griffith [56] and [57], but only goes back as far as the info you already have. It is linked to [65] where it shows marriage of Margaret Mary Roberts, Tyddyn Ysguboriau to John Ellis, Glanllyn, Morfa Bychan, uncle of my grandmother. They lived in Morfa after marriage, but later moved to Tyddyn Ysguboriau, and that's how Tyddyn Ysguboriau family became Ellis'.
Emyr