How are the Osgoods related to the Lammeters in Silas Marner?

The Osgoods are in-laws to the Lammeters. In Chapter 6, Mr. Macey tells the landlord of the Rainbow Inn that Mr. Lammeter courted and married Mr. Osgood's sister in Raveloe years ago.
Since Mr. Osgood's sister married Mr. Lammeter, Mr. Osgood is uncle to both Priscilla and Nancy Lammeter. According to Chapter 6, Mrs. Lammeter (the former Miss Osgood) died before Nancy and Priscilla grew up.
In Chapter 11, we see Mrs. Osgood interacting with Nancy and Priscilla Lammeter. The narrator tells us that even though Nancy's relation to the Osgoods is on Mr. Osgood's side, Nancy shares an uncommonly close relationship with Mrs. Osgood. We also learn that Nancy once turned down an offer of marriage from Gilbert Osgood. Despite her grief, however, Mrs. Osgood did not withdraw her affection from her niece.
Later in the story, we discover that Nancy Lammeter married Godfrey Cass.