Hi Bob
I just want to refer to the census links below as I said the 1901 census link I found, May not be a connection as I can not be sure. I would not dwell on this much until you get more concrete backup.
But do hold onto and keep it in your records.
I have found another entry in 1901 but this one I cant be sure there is a connection
http://www.census.nationalarchives.ie/pages/1901/Dublin/Rathmines___Rathgar_East/Leeson_Park_Avenue/1292434/
The 1911 census I think could be Thomas Murphy born 1888 1889 1890, with brothers Peter and Paddy. I note from the census that Peter Murphy (b approx. 1872) is a lot older aged 39 than his sibling brothers and their mother is recorded as Ann Murphy widow.
I would suggest that you have a look at the 1911 census where the murphys are living and look at who are their neighbours maybe you might recognise another surname which might be a family name.
Am I right in saying that Thomas Murphy b approx. 1888-1890 married a Mary Ann Duffy if so I have found a match for a marriage of
Thomas Murphy and Mary Duffy
Year 1921
Jan to Mar 1921
Dublin South
Vol 2
Page 637
You can order a photo copy of marriage cert from GRO Roscommon costs 4 euros, it maybe the right one I cannot say. But the marriage cert will give the names of both fathers of groom and bride, addresses and occupations of both. Its up to you!!!
What I can suggest to you is that you sit down with your relatives and write everything down no matter how small you think it is i.e. someone might say oh yea johnny soso was in the army, was in prison was involved in 1916 rising etc, keep a note of everything .
If you can add anything more do please.
Regards
Genseacher