In records for St. Mary's RC Church Merthyr:
Marriage April 10, 1898
Elizabeth Finn Bethesda St. Father Cornelius married
Daniel Hayes Bethesda St. Father Thomas
Had children bapped
Honora May 15 1906
John April 15 1900
Margaret Elizabeth May 16 1909
Thomas January 24 1904
There was a Cornelius bapped Sep 21 1902 but transcribed copy I have said father Thomas Hayes and mother Elizabeth Finn. Could be transcription error. I have a Timothy Collins who is shown also as Edward Collins.
I do not have access to 1901 census today but is this a possible for your family? Joan