Thanks for the star, Steve! Yes, the 1850-1881 Mary Ellen must be her (not the one in my answer, but the one in the comments). In 1900, Cecilia Dorsey lived with them, shown as 'niece' in the census. In 1906, Cecilia (living at the same 1900 address) married Harry Fitzpatrick. Over the years, Cecilia's siblings Alice Dorsey and Hugh Dorsey lived with the Fitzpatricks. I think they were the children of Mary's brother Peter, as shown on the 1860 Census cited below. I'd have to go back and dig up those records, but that should help tie them all together.