John's first 2 children were Charles, born May 1855, and Phebe, born 1857. I assumed that they belonged to John and his first wife.
However...I cannot locate John with the 2 children in the 1860 census! There are a couple of faint possibilities...one being a family with very similar names living in a resort town ["Mexico"?], upstate New York.
Then I came across the statement in the "Brooklyn Daily Eagle", that John Hempstead, nephew of the notorious Emma Augusta [Hempstead] Cunningham, in 1857 languished in the Suffolk County jail on charges of bigamy!
John's son Charles turned 2 years old in 1857; his daughter Phebe was just born that year. Did he marry Mary Walton in 1857, while still married to the first wife? Or did he marry someone else before marrying Mary [as his 3rd wife] by the 1865 Riverhead census?
It appears that John's first 2 children considered Mary Walton their mother; I believe her name appears on the death certificate of son Charles Hempstead, and appears so in other people's genealogies. I am not certain that is correct; just have to prove it, one way or the other!
- check Bklyn church records for John's first marriage
- try to obtain court records of bigamy charge
- try to find marriage record, John to Mary Walton