I noted that your Catherine's first daughter was called Anne !
Another loose link to the Anne Cullen possibility.
Where have you been looking for Catherine's records ?
IF she was born in Kingstown, the only real place to look is on IFHF, but they currently only do a months subscription for €30.
Her birth may not have been registered !
She was born very close to the beginning of civil registration in 1864 so a lot of people were not yet in the practice of getting their paperwork civilly registered.
A few other thoughts :
YOUR Matthew may be neither of the gentlemen on the 1901 Census, it's very possible that he died before then.
Also, re the occupation, you have Matthew as a Butler in 1886 ~ 15 years is a LONG time. He may have gone on to learn to be a Range Setter by 1901.
As I say, just a few thoughts and possibilities !
Tara