Hi Dave,
These 3 came up with surname O'Brien mothers maiden name Davies.
Year 1924
Muriel O'Brien
District Merthyr T
Apr/May June 1/4
Year 1925
Eileen m O'Brien
District Cardiff
Oct/Nov/Dec 1/4
Year 1926
Lilian O'Brien
District Merthyr T
Jul/Aug/Sept 1/4