If your ancestor had more than one spouse, consider the possibility that the spouses were siblings.
It was not unheard of for a widower to marry a sister of his deceased wife as his next wife. Sometimes the different wives can be merged into one individual–after all the maiden name of each wife is the same. This can easily happen if the first names of the wives are similar.
Occasionally a widow may marry a brother of her deceased husband as well. In this case the subsequent marriage may not be noticed as the last name of the newly married former widow does not change.