I too am marrying into the McGarrigle Family.My finace John Joseph is beleived to be the IV (that's as far that can be remembered). John's Grandfather II lived in Philly(or right outside of Philly) who worked on the docks and John's (III) father I beleive was born in Philly but moved to Raritan NJ in the late 1920's (His father II passed away in 1930's of pneumonia).
John's father was born in 1923 and only had one brother named Eugene McGarrigle. Eugene had no children.John's III father was married to Linda McNelly and had two children John( my finace) and Lynn Finn(McGarrigle). Please let me know if this helps anyone.John Joseph III is still living and is the only one left besides an Aunt/Cousin that had given me this information.