Hi,
Now since I started looking at the records today, this has been niggling at me so I will post it for others to give their opinion.
Here is a marriage from NSW records
In 1889 DOYLE Joseph to BOLGER Catherine J. at Ashfield reg. 2133
Here is abirth
In 1889 DOYLE Frederick C father Joseph mother Catherine J at Petersham reg 6510
Here is a divorce.
Reg no. 5923.Year 1907 Petitioner DOYLE Catherine DOYLE, Joseph Frederick.
It is possible there was a previous marriage for very young Catherine I think.
She married under her maiden name for the second time if that is the case

Sue
Adding .The son, Frederick Colin Doyle appears to have died in 1961.
Adding also. There is I have discovered, another Catherine J. Bolger on the records in NSW and the above events are very likely hers , not the Catherine we are looking at.
Ah Well, the intracies !!