Looking for more information on John O'Brien from County Cavan

I am looking for any additional help please with John O'Brien. I have hit a brick wall!   I know that John O'Brien married Catherine Connor/Connors/O'Connor March 7, 1857 in Annagh,Belturbet, County Cavan.  His marriage registry entry listed him as Johannes O'Brien and she was Catherium Connors.  John was born 1837, Catherine 1841.

I am having trouble finding the family of John O'Brien and Catherine Connors.

Since John and Catherine married in County Cavan, I am assuming that they were both born and met in the same area.  The only  record I can find for John that makes sense is one I found for John being born in Drumalt, Killashandra, Tullyhunco, County Cavan in 1841.

I could not find an actual birth record but found a 1841census listing of an O'Brien family  with John O'Brien as the father, Bridget O'Brien mother, Francis,Patt,Edward, Margaret, Catherine Gray(sister) John Gray and John.

I am trying to make sure this is the John O'Brien that ties into my family tree.  Would anyone be able to find a birth record ?   I am thinking this may be part of my family tree because there was a Patrick O'Brien listed as a witness at John and Catherines wedding and there is a Patt listed in this family.  John and Catherine had a child at the end of 1857 and had approximately 2 or 3 more children in Ireland before moving to scotland betweeen 1861-1870.  Someone was kind enough to find out the irish childrens names for me, helping me with another brick wall!

I also cannot find any family history for Catherine Connor.  she is listed in many records as connor,connar,connors, O'Connor   I did find a census record for a  Kate Mcconnor  1841 which is correct , in Carrickavee, Castlerahan,Cavan    I am wondering if it would be correct that someone transcribing this information put an mc instead of O'C?  I know that in previous records Catherine s birth was listed in 1841.

I am grateful for anyone's help in any way!!

Linda O'Brien Davitt