I am trying to find out information about my great,great grandfather[,Gerald Featherstone] family (changed spelling to Fetherston later on),Have found quite a bit of info on their arrival in Australia

but would like to know more about their lives in Ireland (Co Roscommon), my g,.g,grandfather married an Elizabeth (Eliza) Dalton and they had three son,one a doctor ,another a ships's captain and one we don't have any information on, The only names I have are Daniel and Michael,who was the missing one?, the boys are believed to have attended Trinity College Dublin pre 1850 but can't get any info to verify this . Would anyone know where to start looking? They also, had a sister think her name was Eleanor (Elenor) who came to Australia for health reasons(she was accompanied by her brother (on the ship's register his name isn't given.Eleanor died from Tuberculosus and is buried at St Felix De Valois Cemetery, Bankstown NSW along with Daniel,Michael
Any info prior to their immigrating to Australia would be greatly appreciated.
thank you genekat