I searched the Irish Family History Foundation's online database. It contains 11,500,000 surviving rcds for abt 60% of Irish counties. Kildare rcds are in the database. Birth and marriage registrations were civil after 1864. For Ballymore Eustace parish: Births..1839–1899, Marriages.. 1839–1899.. Records on microfilm in National Library from 1779.
You didn't state whether you grandfather or his siblings were born in Ireland. This does make a difference. Also, Paddy is short for Patrick; Jim is short for James; Kittie is probably short for Kathleen, Catherine, Kate, or Katharine; Eileen may be short for Ellen. These formal forenames would have been used on civil or church birth/baptismal/marriage rcds.
In any event, I can't find either the formal or pet names associated with Ballymore Eustace parish. However, they do occur in other Kildare parishes. It would help if you had some birth dates and places to go with the names.
Some of this info can be found in U.S. censuses. Suggest you search these and make another post with more definitive info.