HELP! I have fallen into the same trap with William Henry, Sr and the alledged Col John Henry connection. I now see the problem with that premise, as John Henry did not marry Sarah Winston Syme until after her first husband died in 1732. Also, in bios for Patrick Henry b. 1736, it is stated that he was the second child born (presumably after John Syme b. 1729). Other than the above two, all of Sarah's other nine children were born after 1736.
I am working on genealogy for 3 sons by two different mothers who are in different Henry lines. One line goes back to Ola Henry 1907-1956, Benjamin F Henry 1881-1963, Jesse B Henry 1858-1927, all born in Arkansas. Next is James A Henry 1821-1881 of Alabama, Frances P Henry 1800-1853 and Cpt James H Henry (your Malcolm's brother 1774-1839, both of York, SC, and William Henry, Sr of County Tyrone, N. Ireland.
The second line goes back from James P Henry, et al, of east Tennessee and South Carolina on back to a James William Henry, 1726-1796, born in Aberdeen, Scotland. The Col John Henry hoax had both James William Henry and William Henry, Sr as sons of John and Sarah Winston Syme Henry. Back to the drawing board on proving the boys are distantly related. This news will not play well at the Arkansas Henry reunion, Sep 26, 2015 in Mayflower, AR.