O'Sullivan Family from Farnane Franklin, Cappamore

I am trying to find out what happened to the family of Patrick O'Sullivan and his wife Catherine nee Doyle of Farnane Franklin, Cappamore. Their son Michael (born abt 1864),who had emigrated to New York, was my paternal grandfather.
Catherine (widow) was listed in the Irish Census of 1901 and 1911. They had 11 children, but by 1911 only 6 were still living according to the census.
In 1901 sons Denis (41) & Thomas (26) were still on the farm. Neither is listed as there in 1911 but I know that at least 1 of them was still there in 1919.
The 3 children listed on the 1911 Census were the American born children of their son Timothy who had emigrated to NYC. Tim was I'll and had sent them to live with his mother. By 1919 they had all returned to NYC.
Their farm was next to the Leonard family who may have been related - as a Leonard was a godparent for 1 of their children.
I have been unable to find out what happened to Denis & Thomas and would appreciate any information on them and what happened to the farm.
Thanks for any help filling in this part of my "missing" O'Sullivan Family.
Kathleen Sullivan - New York