Hello, I have been asked to look at unanswered queries and have come to your query, it appears that church records on which we rely for this period are not available for Holycross prior to 1835 see https://registers.nli.ie/parishes/0243 So prior to this you will need to find some record related to where he may have worked or been a tenant of some important family whose records may be in the local or national archive but this is unlikely, you could however try the library or archive of the county but they more than likely are not online etc
There are a number of private Facebook pages dealing with Tipperary Genealogy if you use that media and also some Tipperary DNA matching pages also, you must apply to join, usually fairly simple.
I see on Roots a subscription site that there is a John born to Denis Keffe and Mary Fogarty in October 1838 and a Michael born in September 1840, as this is post 1835 there may be earlier children but I now see that Denis Keefe and Mary Fogarty married in 1839 in Holycross on 26th September so first child born pre marriage, not unusual even then, the witnesses are Thomas Keefe and Mary Hogan, remember the marriage would normally be in the brides parish so he may be from another parish but more likely the same as travel was not great then. There is no other information on the record which you could view on the site above.
Good Luck
Pat