Find A Grave Memorial no. 162440710 has "Ada Frances Blackington as a daughter of Francis "Frank" M Blackington & Margaret C Kaler.' https://www.findagrave.com/memorial/162440710#source / The 1860 US Census in Rockland, Maine has two entries for Ada Blackington, b. abt 1851, age 9. The first one is with mother Nancy who is listed as widow, and the other entry is with Francis and Margaret Blackington. I wonder if Ada is two distinct people, or is she the same person? It's possible that 9 year old Ada could have gone to live with the other Blackington family in 1860 because of her age and her mother being single.
Year: 1860; Census Place: Rockland, Knox, Maine; Roll: M653_443; Page: 773; Family History Library Film: 803443
Residence Post Office: Rockland
Year: 1860; Census Place: Rockland, Knox, Maine; Roll: M653_443; Page: 773; Family History Library Film: 803443