Hello from Jaen in Spain

My grandmother Ellen Boyle born 1893 Aughnacloy,married Alexander Harold Robinson in Aughnacloy,on the 1st Dec 1915 in the parish of Carnteel.
On the wedding cert it states that Alexander is illegitimate, a minor, and was labourer.
Alexander , joined the RUC,AND IN 1944,was a Police Sergeant on my aunts marriage at that time.
He died in Liverpool in 1958 aged 60,he was then a Royal Ordinance Rectifier ??.
I have been told that if you were born in a ULSTER COUNTY YOU WOULD NOT HAVE BEEN ABLE TO SERVE THERE-is this correct?
This would then leave me with a hige problem,as how onearth would I find his birth--any help Please.
Regards
Elsa-Mary
Does anyone know of any female Robinsons who might have been his mother?