I am not the historian who contacted your grandmother, however, I have a family history book wherein a gggg grandfather, Thomas Commins married a Lydia Edyvean, who died in 1827, at a fairly young age (I don't know her birthdate, but probably around 1780).I don't think Lydia had any brothers (a reference is made only to sisters).Her father (?)Edyvean lived in Bodmin, which I believe is in Cornwall. From the family history book, it appears that her family circumstances were quite affluent, in that her father "required a certain good income and settlement from each son-in-law, and there seemed small hope of Thomas being able to meet his requirements".Fortunately for Lydia and Thomas, her father died shortly after they became engaged, so they were able to marry.
Lydia and Thomas Commins had three children, two sons and a daughter.Both sons were quite well-off, the first a minister, educated at Cambridge, the second, a lawyer, educated at Exeter.
I understand that if you go back 20 generations, all people of English descent are related!