Anne, follow-up to my previous post
I found a baptism for a John Grant b. 11 June 1808, but his parents were Alex Grant and Anne Cameron. So this can't be the John you found in Alex' will. (But there is a John in St.Andrew's records b. 1830 to Alex and Anne McDonnell).
Whoa! just occurred to me that that answers my question posted on message board: there was another Alex Grant married to an Anne. I wonder if those are my James' parents???
This might explain why James Roy's grandson did not live near lots 25-26 100 years later.
"John Grant son of Alexr Grant of Charlottenburg (South Branch) and of Anne Cameron his wife, was born on the 11th and baptised on the 24th June." 
The wording is exactly the same as the wording for James except that the mother's maiden name is included.
I checked the name of the other child not named in Alex Grant's will. Donald, bap. 5 Jan 1794 is the son of Anne McDonnell. Maybe he died young.
Now I guess I need to learn who Anne Cameron was and where other Alex Grants lived. (sigh!)
[Also found at FamilySearch, baptisms of other children of Alex Grant and Anne Cameron: Margaret, 15 June 1810 and Hugh 20 Feb. 1805. (No James listed there).]