Hi
Your enquiry continues to trouble me. Your original information about your Grandfather, James Patrick McDonald, is derived from his 1911 marriage certificate. In my family the marriage certificates are the most likely to contain misleading information. I have seen wrong names, wrong ages, fictional fathers and dodgy descriptions of occupation. If James was born out of wedlock he may not have known who his father was and to avoid embarrassment may have given his Grandfather's name at the wedding.
All the best
Gobbo