Could you please supply a little more detial:
1 the 1842 census? Which was this and can you link to it please?
2 death dates of the parents
3 siblings of John
4 Confirmation that you are aware of the many many variations of the spelling of the name Keane and have searched on these - Kean, Cain Caine, Kane etc.
5 have you searched on Family Search and Irish genealogy https://www.irishgenealogy.ie/en/
I would do soem searching on FS for you but my computer has decided to speak to me in Portuguese only...while I am able to make my way as a tourist in portuigal my skills are not up to reading BDM entries in that language.
The 1842 Census was recorded by a member of the Clergy here & not on line
Dont have death dates for Parents as I imagine it was prior to Civil Reg
Siblings of John were Mary Anne & Catherine
I am aware of all the variations of the Surname
I have searched all available sites no results I also thought John may have immigrated as it was during the period of the Famine in Ireland when many people left the country.
Thank you