Thanks! Obviously my 4th Great Grandfather is number 2. He would had 3 sons and 2 daughters by 1796. The final four more children were all born between 1800-1805. But his first 5 were 3 sons and 2 daughers. Additionally, since 'Lunenburgh, or the Old Eastern District' lists him as one of the first settlers of Upper Canada, the fact that the other two died during the war would have made him the only Alexander Grant to be a Veteran and Settler.
In March 1786 he makes a "Memorial Claim" for 100 acres held on lease from Sir John Johnson, house, horses, cattle for being a veteran of the King's Royal Regiment.
I would still really like to find out who his fater was for sure.
But thank you so much for finding this out for me.