I missed the Margaret Cain living with Harriet (Cain, sisters) Caswell on the 1860 census. However, my speculation to this is that Margaret "Maggie" Cain moved from house to house, taken in by family.
Harriet Cain was on the 1860 census twice in two different places. Both times the same age, both times with a child named Temperance, same age.
I don't think they had a very stable life.