John,I wonder if you know where in Ma your Sheehan family lived in 1870?
I know of a Sheehan family that lived in Salem MA (at least in early 1900's and conceivabley before that).I know they had at least two daughters (Grace who never married dob aprox 1905 - 1908) and Helen who married someone named ? Walsh. and was living with her father(he could be a widower) around 1920-30.
I think they lived on Dunlap street in Salem, or Varney which is in same area of Salem. Grace was a very special freind of my late mothers.