If you are looking for current families you could try
writing to the Callan's in the Kildare telephone book which is on line, there are 13 but only 3 in the Nass area.
There are over 200 O'Brien's but if you go through them
carefully you probably will find a few you could send letters to but leave that search to the end as there are only 9 Bourke's. Its worth a few stamps.
The posting about Callan has been answered. It is harder to find current family members than older ones.
You can use the 1901/11 Census for the addresses to compare to the phone book or a good map.
Nass, the civil registration district would cover an area of
12 miles from the town and contain as noted parish's, and villages and smaller towns.