O'Brien/Brien

Lyn,

What year was William born?

Do you have his marriage or death record.

Nothing found for Owen O'Brien or William O'Brien in County Kildare 1830's/1840's.

Regards,

You may already be aware of them, but there are records for what appear to be William and his parents (as well as William's descendants) in the FamilySearch database:

https://www.familysearch.org

If you search there, you can find William under ID number KLLY-7BY, and can access the records for the others easily through that record, as you will see.  Those records do not go further back than William's parents, but in each record, at the right hand side of the screen, you can see the screen names of those who have created or modified the record, and can send them private messages, so you might be able to get more info by contacting them (and perhaps also locate some relatives that way).  Jay Follett is shown as the main person providing info in those records, so you might want to contact him.

FamilySearch is operated by the LDS church, and is free to use.  You have to create an account to use the database, but they don’t ask for much personal info, and no missionaries will contact you or anything like that.  The database does not have separate family trees, and is essentially one huge tree of linked records, in which there is a single record for each person, with a unique identification number (although sometimes people unknowingly create duplicate records for the same person, which you can merge when you spot them).  In case you’re interested, you can see more about Athy at this site:

https://www.townlands.ie/kildare/narragh-reban-west/st-michaels/athy/