Thank you for your generosity of time and information.
They moved to Liverpool in time to be counted on the 1891 census. 1891 and 1901 only give birthplace as Ireland. Their third child - Catherine Mary or Mary Catherine, depending on the record-was born in Warrenpoint. Their other children were born in Liverpool. It isn't until the 1911 census that Frederick gives his place of birth as Warrenpoint and Mary gives hers as Camlough. I can't seem to find a birth record for either Frederick or Mary.