aghadowey - yes, I realise this, but I can really only work with what I got. And I have to assume that even if his parents died young, which is what I thought with the John Tobin of the Edmond Tobin blacksmith, he'd still know his birthdate, at least the day and the month if not the year.
myluck! - I thought that at first until I found out the birthdate info. But there's also the problem that I'm pretty sure the Maher is a transcription error for Usher. Margaret Usher had 6 other children with Edmond Tobin, on either side of the John born in 1892. I've not been able to find a marriage certificate for Maher/Tobin or any other children. So I'm pretty sure it was the same family.
I have a paper trail from Margaret Ussher/Usher's birth to her marriage to Edmond Tobin to her remarriage to the Corbett. I'm pretty sure she was an Usher not a Maher. The only thing might be that he was an illegitimate birth and Edmond Tobin had an affair with this Margaret Maher, but no one can find his baptism to prove this. And would she be brave enough to put his name on the birth certificate if it was an affair/illegitimate child?
The reason I need all this info to work out properly is that my British husband's job relies on being an EU citizen. If we can prove his grandfather was Irish he can apply to be registered as an Irish Foreign Birth and get Irish citizenship and keep his job if Brexit should come to pass. So I really need things to be pretty indisputable, even if I need a complicated paper trail to prove it. So I think a different birth date and mother's maiden name will not convince them.
Thanks for trying and keep throwing any ideas at me as I'm desperate. I'm still waiting on the priest from the parish he was married in to check the Chancery records to see if there was any note on his marriage papers about where he was born as he'd possibly have to prove he was baptised as a Catholic to be married. That would give us a place to look hopefully. There was nothing in the registry book so I'm thinking it's a long shot there will be anything else, but fingers crossed.