Incredibly there are two Sweeney Families in Lewiston, Androscoggin, Maine with a mother named Margaret and daughter named Hannah and Mary.
In the 1870 census my relatives are listed a Sweny in Portland, Cumberland and in the 1880 Census they are in Lewiston, Androscoggin with their names spelt correctly.
In my family Hannah was born in Nova Scotia and is older and Mary E is the baby of the family (8 years younger) born in Maine. There is also 2nd oldest Margaret A. (born in Nova Scotia), Hugh and William (both born in Mass.).
I think Margaret may have married Michael Doherty but the age and parents’ names don’t match.
I believe the family you found is the other Sweeney family that was in the area.