Well done myluck, I was about to look at the CWGC website when I received your communication. Cathy, they were both attached to the Royal Dublin Fusiliers - Michael was in the 2nd Battalion and was killed on 01/07/1916, the first day of the Battle of the Somme. His grave is unknown, but is commemorated on Pier and Face 16C, Thiepval Memorial in France.
There's a J. Dunne of the Royal Dublin Fusiliers, 1st Battalion, also killed on 01/07/1916 and was buried at Grave A. 92. Hawthorn Ridge Cemetery, No. 2, Auchonvillers, France. In his case the CWGC records do not give his home address, but there's a good chance that they are your uncles.
Now, I cannot find Michael and Catherine Dunne of Stonybatter or Grangegorman, on the census for 1901 or 1911, but it doesn't mean they are not there. Will you look up the national census on
http://www.census.nationalarchives.ie/ and see if you can locate the family? This would give you a clue about the names of your other uncles. In the meantime, I will try to find their Service Records over the next few weeks and contact you again.
Ken.