I'd look in Wood Green Middlesex, England. According to his find A Grave memorial # 91461810 that's where he was born.
All census records I have seen for William Humphrey show that he was born in Virginia. According to:
"History of the Upper Ohio Valley" Vol. II, 1890. Presented by Linda Fluharty from hard copies provided by Mary Staley & Phyllis Slater. Page 517. It says he is of English descent, but not that he was born in England. Find-A-Grave owner is non-responsive on providing any proof of birth in England. My research also shows additional children. No luck on parents for my 3rd Great-Grandfather. I am willing to share any info on his 21 children.