Here's the details of the extracted birth record you mentioned :
Name: John Page
Birth date: 29 Jan 1876
Place: Halvastown, Kildare
Parents : Joseph Page / Julia Bryan
and this looks like like the corresponding civil index record :
name: John Page
registration district: Naas
Event type: Birth
Year: 1876
Volume : 2 / Page : 930
The townland of Halverstown in the district of Nass and nearby Calverstown townland and Demesne, seem to be located in the civil registration district of Athy.
There are two possible siblings of John on the extracted records :
Name: [Male] Page
Birth date: 17 Feb 1872
Birthplace: Newbridge, Kildare
Parents : Joseph Page / Julia Brien
Name: James Page
Birth date: 05 May 1878
Birthplace: Newbridge, Kildare
Parents : Joseph Page / Julia Bryant
I dont see any likely marriages for for Joseph and Julia - maybe they married before the start of full civil registration... what's the age of their eldest child ?
see:
Introduction to Irish RecordsShane