For Cat(herine) Lehan, I found only 5 B rcds in Ireland: 1792 Cork, 1793 Cork, 1809 Cork, 1825 Cork, and 1842 Cork. Only the last has a chance of being for this ancestor. The surname LEHAN is rare in Ireland. This is the first time I have seen it.
For Pat(rick) Nevin B ????, somewhere in Ireland, with the father's forename unknown, I found 263 B rcds - waaaay too many to easily summarize here. There are 27 rcds in the range 1850 +/- 5 yrs.
Suggest you search the censuses to find some est DOB for these two to narrow your search.