Thomas Dempsey - Mariah's brother?

We know from her siblings' obituaries in NYC that Mariah had a brother Thomas. (Why no obits in Irish papers at this time?). And we know that he stayed in Ireland.

From Baptism records we know the children of Bernard Dempsey and Catherine Jennings were:

Mariah / Mary  - born 1854 - stays Ireland

Patrick - 1855  from  Ballintubber records

Thomas - 1857 from Ballintubber records - stays Ireland

Brigid  - 1860

Bernard   - 1862 - to UK

Anne   - 1864 

John  - 1865 - to US

Michael   - 1867  

Martin  - 1868 - to US

Catherine   - 1870  - to US

So, somehow Bernard and Catherine were in Ballintubber for the birth of two of their children.

We don't know what happens to most of them, but we do know that Catherine, John, and Martin go to the US when their father Bernard dies in 1871. Bernard (Jr) goes to the UK.

Thomas stays in Ireland, but is NOT one of the MANY Thomas Dempseys in the Cloonreliagh area.

Did he marry and move to a different area?
Here's a Thomas Dempsey in 1911 census in Leitrim, born in Roscommon.

http://www.census.nationalarchives.ie/pages/1911/Leitrim/Yugan/Annagh_Upper/648053/

Note, they are also present in the 1901 census in the same townland, but it does not note his birthplace as Roscommon.

I can't find the marriage record for their marriage, but Thomas's wife Bridget dies in 1916: 

https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1917/05221/4444748.pdf

He re-marries in 1917:

https://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1917/09762/5543252.pdf

His father? Bernard! Is this our Thomas?

Thomas dies 1944. Francis Earley present at death. No mention made of a relationship to Thomas.

https://civilrecords.irishgenealogy.ie/churchrecords/images/deaths_returns/deaths_1944/04643/4234068.pdf

Note: Registration District for above is Carrick-on-Shannon.