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The 1911 census for Slievenabrehan shows that either John or Thomas was deceased by 1911. http://census.nationalarchives.ie/reels/nai003000460/
I would suspect John. I would check the English 1911 census to see if you can find Thomas. By the way, your grandfather was born in April 1894. I also located a 1932 death record for the father but did no locate a record for the mother Ellen.