It's a similar situation with me. I was born and bred in Cornwall. My mother's mother was born a Trethewey and her mother was a Davy. I don't know their first names. I too was told we were related but like you, I've never really made the effort to delve any deeper. One thing is certain; there are no direct descendents of Sir Humphry as he had no children, so any connection would be through other members of his family.