I have a Julia Donovan born in 1775 in Ireland, passed in 1820, also in Ireland. The closest location I can find her would be through her spouse, Cornelius Sexton from County Cork Ireland. I have hit a dead end with both of these, but haven't given up in the 12 years I've been searching for them! They had a son, Jeremiah Sexton, who immigrated to the US, and ended up in Indiana County, PA, with the first record I've found is a marriage record to a Mary J. Mswiney in
July 5, 1856
in INDIANA, PA. Her ancestry is also from County Cork, but they immigrated to Lycoming County PA, then on to Indiana County PA between 1805 and 1832, where I find a marriage of immigrant MicSwiney in the US.
My only link to the Donovans I've found is Julia in Ireland. I don't know if you could start with her (Donovan-905) and work your way around those dates and areas, and hopefully they may lead you to your John!