For John Banks B ???? in Co. Leitrim with a father forenamed Pat(rick), I found 1 rcd in 1872, Drumlease RC parish. A view of the B rcd SHOULD show both parent's names and MAY give you hints on their residence and origins.
POSSIBLE siblings to John are Catherine 1888, Mary 1889, Margaret 1893, & Patrick 1891. Normally, I would have expected to find several B rcds around the 1872 date for John.
For Pat(rick) Banks M 1868 +/- 4 yrs somewhere in Ireland, I found 2 rcds: 1869 Mayo, and 1869 Limerick. Mayo is closer to Leitrim than Limerick. For Co. Mayo, Killala is the registration district. Since the rcd for John was RC, I would have expected to find Patrick's rcd in a RC parish as well, especially because it occurred close to the start of civil registration when most people generally did it both ways.
All of the above is very tenuous - your info was especially sketchy.