Denise,
One correction to what I said above about Templenoe...it is not a town land. The RC parish of Kenmare is also known as Templenoe and Dourus as well. So, on the marriage record for the two couples, it has address as either Kenmare or Templenoe, I think they are just referring to the larger parish, and the exact town land is not given as it is in birth records. I believe that your Ancestry tree (Sullivan/Tubman..if that's you) has Mary Brennan as their mother. The only problem I see with that is the length of time between their marriage and their first born son, Patrick. Even the gap between the other couple and Patrick's approximated birth is a longer time than usual....although miscarriages and infertility are possible.
I did find three of the five births to Eugene Sullivan & Mary Sullivan (her maiden name):
Denis, address Gurtbrack (Templenoe) 6 Aug 1837 to Eugene Sullivan & Mary Sullivan, sponsors - Denis White & Mary Cronin
Margaret, Gurthbrack, 5 Nov 1843, same parents, sponsors - John Sullivan & Margaret Sullivan
Mary, Gurthbrack, 3 May 1846, same parents, sponsors - John Sullivan & Catherine Sullivan
Cannot say with certainty that these are your relations, and I could not locate Patrick or Sylvester.
Keep in mind that self-reported birth dates are approximated, and many folks did not know the year they were born as we do today; and it was not uncommon to change one's year of birth upon immigration - for a variety of reasons.
Regards,