Hi Babzi,
Thanks for getting back to me. Frederick and his past have been a pretty solid brick wall for me, but hopefully I'm starting to crack it. I only recently found out about Robert through articles in the Freeman's journal which made references to his brother Frederick. The dates, place, job etc all tie in (as well as the fact they are mentioned several times as brothers) to make me confident they actually are brothers.
Thank you for this information, I'll have a dig around to see if I can find a connection with John and Ellen. It doesn't seem to be a common name in Dublin at the time and if they are in the same parish, they must be related somehow.
Thanks,
Angel