AncestryDNA has confirmed my relationship to Joshua Burrill, father of Sophronia (Burrill) Leonard-Knapp. Sophronia married Russell Leonard, who left her and two small children in central New York to go buy land in Michigan in 1833 and never returned. To this day, we have no answers about his fate.
Sophronia's parents were Joshua Burrill and Caroline Fitts. Caroline was born on August 4, 1786 and married Joshua Burrill "formerly of Edmeston, N.Y." Caroline's sister, Roxilana, married Joshua's brother, John Burrill.  They were descendants of Lord Burrill of King's Deer Park of Wales.  Joshua was a hotel keeper in Onondaga County and in Righville, Genesee County, New York, according to Fitts Genealogy. (No place called Righville or any similar name in or around Genesee County can be found. If anyone knows what place the author was referring to, please comment below!)
Fitts Genealogy names only four of Joshua and Caroline's children:
Martha aka "Patty" (1810-1869), who married David Redman and had 12 children.
Achsah (1814-1884), who married John King and had 4 children.
Arba (1813- ), who married and had a family.
Mahaleth, who married and had no children.
Other known children were:
Brooksey (1812-1902), born Nov. 14, 1812, in Middleborough, Plymouth, Massachusetts
Sophronia (1814/5-1883), my ancestor.
I have found no evidence of Sophronia's birth, and no proof of her connection to Joshua Burrill, except DNA matches with several of her siblings' descendants, which can be seen here. If you have any information about Sophronia, please share!
Regarding Caroline Fitts' family, below are more excerpts from "Genealogy of the Fitts or Fitz Family in America", showing Caroline's lineage.