Margaret Byrne as witness
At the time of 1939 register of electors 4 Moran's Cottages was occupied by a Thomas and Mary Byrne two very hard name's to research in Dublin,i cant seem to pick up 4 Moran's Cottages on the Electoral Rolls 1912 to 1915 maybe someone else here may be able to do so.
Timothy,Bertha and Josephine seem to be at 1 Rathgar Road in 1939.
Have you tried contacting the church ? where they were married in 1915 to see if you could get her mothers name.
I personally have had some success visiting the church where some relatives were married as late as 1940s but not all are interested in providing this service ,a lot dont even acknowledge emails or letter's even when offering a fee for this service but as i say nothing ventured nothing gained.
Dathai.