'Much information has since been found about John Benedict, son of Joseph. He was born in 1739 [citing King's Royal Regiment of New York by Brigadier General, Ernest A. Cruikshank. Ontario Historical Society, Toronto 1931]. First mention of him was when his father, Joseph, died. The will was probated in Woodbury, Connecticut, in 1759 making "his youngest son John Benedict," his executor.'
While his birth year is given as 1739, his mother (if Mary Groom) was at least 48 by then. It is possible that Mary had died and his father remarried, but given that John was named as his father's executor in 1759, he was likely at least 21 by then, so a birth year of 1739 is suspect anyways.