The father of the John Kenny married in 1864 was John based on the civil marriage record. see last record
In 1855 John Kenny was in Tonroe and Feenagh based on the Griffiths Valuation head of household listing https://www.failteromhat.com/griffiths/roscommon/kilnamanagh.php
The records for the RC parish of Ballinameen (Kilnamanagh) start in 1859. Earlier records were lost.
From the 1837 Lewis Topographical Dictionary entry for Kilnamanagh parish we know there was a chapel there in 1837. https://www.libraryireland.com/topog/K/Kilnamanagh-Boyle-Roscommon.php
From the 1833 Tithe listings for Kilnamanagh parish, we know there were records for a John Kenny Pat Kenny and Peter Kenny in Tonroe.
Unfortunately, I don't believe the 1831 marriage record or the 1838 baptismal record are for your ancestors.
Your best bet is DNA testing other than the Y test. Have you taken an autosomal test?
Let me know if your have questions.