Hi Phyl
Sorry for the delay - I no longer work for Ireland XO and have been having issues with personal email so only getting back online just now.
I see that the surname of the family is spelt differently between 1901 and 1911, Reilly in 1901 and Rielly in 1911 - something to think about when it comes to online searches.
You could take a look at the free records available on irishgenealogy.ie as they will have (where available) marriages up to 1940 or thereabouts and might be of use to see which of the children of Martin listed on the Census married. Look for the girls first, as they will more than likely have married in Tuam, their home parish.
As 4 of the 8 Reilly children on that Census were deceased by 1911, you could also use irishgenealogy to see if there are any civil death records for them. Civil deaths where they exist are recorded up to 1965.
There is a death record for a Mary Reilly formally of Barrack Street. I searched irishgenealogy between 1907 (the year of Rose's birth, their last recorded child) and 1911 (the Censuss year where Martin states he is a widow) and located this record entry No. 134. This Mary is listed as a wife of a Labourer and Martin is recorded as a Labourer on the Census. The entry though refers to her death aged 46 in Tuam Workhouse. She is listed as married. Mary is recorded as dying on 14th March 1911 and the Census of that year was taken on 2nd April 1911, leaving Martin a widower on that Census Return. It could be that this is Mary, Martin's wife.
I note that Jerard (or Gerard) as he is listed on a birth records (and who is recorded with a brother Thomas, a relative on the Census 1911), is the son of a Michael Byrne and Margaret Tuohy, perhaps then making Margaret (Maggie) his mother, a sister of Mary Reilly and these boys then nephews of Martin Reilly through their relationship with his wife Mary? If this is the correct birth record for Jerard it would seem he was born in Tuam workhouse. Michael Byrne and Maggie Tuohy were both from Barrack Street and were married in 1904. I wonder if the Census entry should actually read 'sister in law' for Maggie and not 'step daughter' in terms of her relationship to Martin, the head of household?
I will leave you to ponder! I will keep an eye here and will receive a notification of any reply you make in any case and won't be so long in replying next time.
All the best
Clare