My ancestor, Thomas Usher, married an Ann Williams (aka Williamson) in 1868 at St John's, Seaham, County Durham. They are listed together in 1871 in South Hylton. As far as I know they were childless.
Thomas is then listed with Hannah (nee Brigham) in 1881, with his two sons, one of them my ancestor.
My first thought was that Ann had died and Thomas remarried, but I have since discovered she actually married a John George Small (father John Small) in May 1881 (after the census taken in April) in St Andrew's, Dalton-le-Dale, Seaham. She states she is a widow on her marriage record, but Thomas was still living, which is something I've learnt a bigamist may do in order to remarry.
I have not searched for divorce papers for Thomas and Ann, but I cannot find a marriage for Thomas and Hannah and I don't think they ever were married. Their son, John William, actually married as, died as, and had children by the name of Brigham, thus taking his mother's name. His brother died young and his two sisters took Brigham as a middle name even though they weren't registered as such.
The above leads me to think that Ann was a bigamist.
The trouble is, I can't seem to find Ann in 1881 or any census thereafter and wondered if anyone could take a look incase I'm missing something? I'm not even sure if John George Small was her second husband's real name as I can't seem to find any birth or death records that would match up to his marriage date.
Any help would be much appreciated, folks. Thanks

PS. Ann was born in Moorsley, County Durham in 1848.