you might get a better response if you post in the Dublin forum. A quick look at the available church records on the IFHF site shows 2 John Flanagans with a father Thomas. Both born in the St. Pauls, Arran Quay parish of North Dublin Diocese. One in 1830 the other in 1832. Possible the 1st John died and the next boy was named John again, this often occured where a baby died. The Dublin city Church records aren't available online yet as far as I know (I'm open to correction). The fact that Thomas was a farm labourer suggests he was not in the city centre. It could also mean that he moved around a lot as labourers tended to follow the available work & all births won't show up in the one parish.