Cathy23
The link i gave you was for (Catherine) in St. Michaels RC in Kingstown so it is a baptismal record, though it does give the birth date 26.03.1867. Baptised on 05.04.1867
sponsors: James Dunne and Mary Brennan?
here is the link for the earlier child MaryAnne:
http://registers.nli.ie/registers/vtls000633812#page/57/mode/1upsame church - birth date 09.02.1864 Baptized: 24.02.1864
sponsors: Robert Lenihan and Mary Stack?
perhaps the sponsors names may mean something to you.
This is based on parents being Matthew Comerford & Annie Cullen in Kingstown.
There is a Mary Anne Comerford birth reg. in 1864 Rathdown available from GRO
V.2 P. 807 District: Rathdown
I would also give the suggestion from Dathai re birth for Catherine born in Dublin North 1867 a shot, as its possible the birth could have taken place there in hospital?
Good Luck
