Sometime in the middle of the 19th century, a Mrs. Harriet I. Nesbett wrote a brief history of the early settlement of Grafton. The Nesbett family were early settlers of the area. Mrs. Nesbett's history of settlement was published in an 1879 History of Lorain County. Perhaps she wrote the article expressly for the 1879 History, or perhaps at an earlier time, but, in any event, she was credited with the written article. Both the Sibley family and Franklin Wells are mentioned by her.
According to the history, the Stephen Sibley family arrived from Massachusetts in the 1816/1817 time frame. The family consisted of Stephen Sibley, his wife, and five grown children. The children were sons John, George, and Giles, and daughters Nancy and Mary.
A year or so later, Franklin Wells, also from Massachusetts, arrived. Initially, he taught school in Grafton, was elected Justice of the Peace, and became an Associate Judge in Lorain County. He married Mary Sibley in 1823.
Stephen Sibley's death occurred in the spring of 1829, at about age 70. Prior to his death, his son in law, Franklin Wells had assumed the care of the homestead.
The above info would seem to clearly indicate that Mary Sibley's father was Stephen Sibley. A clue to her mother's name can be located at the Ohio GenWeb site for Lorain County:
If you look under the heading "Cemeteries" you will find transcriptions from most of the cemeteries in Lorain County. In the Belden or Old Grafton Cemetery, can be found a couple of Mary Sibley's brothers, and her mother Jemima. The stone is inscribed, Jemima Sibley, wife of Stephen, died January 1,1836, age 80.
Additionally, someone has posted a family tree on the internet for Mary Newton Wells, who was a daughter of Franklin Wells, and Mary Sibley. The info given for Franklin and Mary agrees with the info included in the 1879 Lorain County History --- but also takes both families back several more generations. Accuracy of any info posted on the net without validation is always suspect, but the info seems well researched, and is at least a good starting point. The site is;