John Campbell, born approx 1776, Loughgilly

I am searching for the county and parish of my ancestors, John Campbell and his son William Campbell, both born in Ireland.  My John Campbell was a pensioned soldier, retired from the 11th Royal Veterans Battalion, who received a Canada land grant in Simcoe county, Ontario, Canada in 1831.  I found a John Campbell, pensioned from the 11th Royal Veterans' Battalion in 1814 at age 38, who was from Loughgilly, Armagh - and am wondering whether he might have been my ancestor.  My John Campbell was married to Elizabeth Weir (not sure of the last name, because of the handwriting).  She was also Irish and their sons, William, John, Richard and James, were also born in Ireland and immigrated to Canada with their parents.  Records in Canada show them to have been Wesleyan Methodists.   If anyone knows anything about John Campbell of Loughgilly - and can either confirm or refute any connection between him and my ancestor, this would be greatly appreciated.    Catherine Campbell, Ottawa, ON, Canada