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I assume you know that Margaret had two older sisters and two younger sisters. The family lived in Cloonca townland in Kilmacteige civil parish when the last child, Winifred, was born in 1879. I searched on the subscription site Roots Ireland and located a possible baptismal record for John Reid. See below. I did not find a church or civil marriage record. The marriage occurred pre-1870 and I'm wondering if Bridget was from Co. Mayo which borders Kilnmacteige parish and there are a couple parishes which do not have marriage records back to 1870 or earlier e.g. Atttymass.Bridget died pre 1901. Here is the 1901 census record http://www.census.nationalarchives.ie/pages/1901/Sligo/Breencorragh/Cloonca/1687437/ John died between 1901 and 1911
http://www.census.nationalarchives.ie/pages/1911/Sligo/Breencorragh/Cloonca/772263/ I was unable to locate a death record for either Bridget or John.
Name:John ReidDate of Birth:
Date of Baptism:10-Jun-1849Address:CarnagopalParish/District:KILMACTEIGUEGender:MaleCountyCo. Sligo
Sponsor 1 /
Informant 1:Gerald BurkeSponsor 2 /
Informant 2:Ellen Roddy