There are few records for birth's for Cavan and those are
hit and miss at best.
The Title Valuation (census substitute)of the 1820-30's might tell you where in Cavan they lived. These are available at the national archives in Dublin or on ancestry.com
The Griffith Valuation 1850's is also a census substitute
which if you cross reference the Parish's for the Farley/Brady families you might find a common parish.
Once you have a few parish's in common you go towww.from-ireland.ie
and look for the RC microfilm of parish's and see what years that would contain the years you are looking for.
There were 57 Farley and 1,323 Brady families in Cavan of 1857. You would need to cross references the parishs. You will have more patience than me.
I would start with the Farley-Parish's and then tick of those of the Brady's, then look for the Cavan RC Parish records on www.from-ireland.iewww.failteromhat.com
for cross referencing Parish's
There are 45 Farley's in the current phone book for Cavan
you can use the refine search for common place names with the Brady's, 383 both surname and letter's B. names I looked at the first 3 pages 60 phone and addresses.www.censusfinder.com
+ Cavan sometimes these are the source of good information depending on the county.
if you want to see more details www.askaboutireland.ie