Baptism record for Robert Doherty born c1826

Hi 

Looking for a baptism record for ROBERT DOHERTY born c1826 in Limerick (I believe)

His father's name was JOHN DOHERTY. Mother's name not known. Siblings names not known.

It is believed Robert may be related somehow to CHARLES DOHERTY born 1790 in Rathkeale. Charles served in the 28th  Regiment at Waterloo)

At age 40, Robert  married ISABELLA KEAYES (Keyes/Keys) on Dec 6 1866 in MUNGRET, LIMERICK

They had 6 children: Robert b.1860, Catherine b1864  Mary b1866  Charles Albert b1869  Philip b1871  Edward b1872.

Except for Robert jr they were all baptised at ST MUNCHINS CHURCH OF IRELAND LIMERICK

Robert was a Sergeant in the 30th Regiment British Army until 1855 then a Sergeant in the County Limerick Militia 1864-1873.

He died in Limerick in 1873.

I have searched countless genealogy websites unsuccessfully to locate Robert's ancestral line.

Any assistance would be most appreciated.

Many thanks

Aussie Doherty