As Valentine is an unusual name, and judging by his age and ages of his parents he may have been one of the older sons and perhaps called after a grandfather, I checked Griffiths' Valuation for a Valentine Ryan in Co. Kilkenny. There were 2.
1. Union: Waterford; Parish: Killahy; Townland: Inchacarran; Place: Inchacarran.
2. Union: Thomastown; Parish: Graiguenamanagh; Townland: Graiguenamanagh; Place: Douske Lane, South of High St.
These people may have no connection to the Ryan family in Manchester but should be noted as being of interest.
Griffiths' Valuation was a survey of property holdings in Ireland. It was undertaken in the 1850s, a few years after the Great Famine. There are lists of property holders in each townland with accompanying maps. Griffiths' Valuation is free to look at. Ryan entries in Kilkenny on Griffiths number approx. 2,500.
"Union", "Parish" and "Townland" are units within a county. A townland is not the same as a town. Smallest unit is townland. They vary in size. (If your ancestor put name of townland on census you've got a head start.) A parish in context of Griffiths Valuation means civil parish. A Union was a group of parishes. Unions were set up in Ireland to administer the Poor Law, introduced to the country 1838. Unions were later used in organisation of civil registration of births, marriages and deaths.
(This is 2nd time I've typed this. I clicked on wrong thing and wiped 1st go.)