One would not think a local priest knowing the distinction between two families would have made such an error but somebody may have been hard of hearing or absent-minded and have transposed names or otherwise made errors, as Frank suggested. Errors that you think possibly couldn't happen do occasionally happen.
According to Edward MacLysaght's books, Cronin was a sept in the ancient Corca Laoide (largely west Cork). They were erenaghs (tithe collectors) around Gougane Barra, an area which is sort of on the border of Cork and Kerry west of Macroom and north of Dunmanway. There were several small Ronan/Ronayne septs in Ireland. They seem to have been clustered in Mayo, Dublin, and east Cork. Hope that helps.