Quinn - O'Brien - Cummins [Kilnaboy, Clare]

[Verlorian]

Hello,
I just recently found my 2x great Aunt Bridget's (1859-1846) information in the 1901 and 1911 census online.
In 1901 while my 2x great grandfather Peter Quin (1820-1910) was still listed as "head",  my Aunt's 2 sons had the last name of Quin also. In the 1911 census after my gg-grandfather's death, the 2 boys are listed with 2 different last names [Martin O'Brien (1888) and Michael Cummins (1896)]. They also used both O'Brien and Quinn over the years for registering various relatives deaths, and a 1918 prison stay for Martin O'Brien.

Are there any guesses as to why this would be, or could it be I am looking at 2 different families with huge coincidences?

Any opinions would be welcome & thank you,
Laura

[Sinann]

1901
http://www.census.nationalarchives.ie/reels/nai000460425/
1911
http://www.census.nationalarchives.ie/reels/nai001747258/

A few thoughts
Peter couldn't fill in the form himself so we don't know how the conversation went with the enumerator, he may have assumed the boys surnames.
Peter may not have liked the boys fathers and refused to use their names.
It may simply be a case of mood on the boys part as to if and when they wanted to use their mother's name or their father's.
Also again Bridget couldn't fill in the Census form, perhaps the person filling in the form knew the family well enough to know the boys father's names.

If you look at the house and building return in both 1901 and 1911 the landlord is Naylon, so I think it is the same family in each census.

[Verlorian]

Thank you for your suggestions, I was thinking along those lines as well.
I didn't know about the house and building though, so again, thanks for that. It didn't occur to me at all to look at that, and will keep me going in that direction.