Hello John. I’m new here. I came across this thread as I’m researching my family tree. Cornelius was my 4th Great Grandfather on my dads side of the family.

I believe Cornelius was one of four siblings of Richard Brain (1761-1831)

George
Ephraim
Mary

I hope this helps.
Any further information you may have on the Brain family would help or any distant relatives of mine I would love to hear from you.