presuming that they were not children in 1929 they should be listed on the 1911 census
I searched for Timothy DILLON of all ages and found there were 13 in Ireland
There was only one in Co. Clare at Residents of a house 1 in Booltiaghadine (Killinaboy, Clare)
living with his widowed mother, Bridget, and six siblings that includes a John
If you look carefully at the census paper Bridget seems to have stated how long she was married and number of children but it is rubbed out. I thick it read 9 children which would give hope one was a Martin!
LINKThis is the family in 1901
LINK however the father's name was also Timothy