Thanks for your message, sorry for delay in replying. I was pretty sure that there were no GERRARDs from India, but checked my files and databases to make sure. I also checked out British Library - a basic search for the names you gave me, as the BL has most of the colonial Asian records, nothing found but not all their records are online, so maybe you could contact them for advise. Also checked TNA, Kew, they have some indian records - usually under East India; had thought their military records would bring something up,- again not all is online. A more thorough search of the catalogues is needed to find the right sub-section.
I had a look on Ancestry and found many John Grant GERRARDs no doubt you have too. There was a John G who married a GRANT in Wiltshire, which quite excited me as my line originated there way back, but realised that M was too late. Also checked a no. of trees and found two conflicting sets of data, one with John G Sen born in India and the other Ireland. Having looked at the marriages of JGG's children noted many carried the wifes surname as a middle name - which tends to be a trend in my line also. but no link to a GRANT. Have you tried to establish where the name GRANT came from?
I will be happy to hear from you and will see if I can find anything more. My feelings are that your JG probably originated in either Lancashire or Ireland, and that pursuing the Military link may prove worthwhile.