Years ago, I had a researcher search for the marriage of William Newman and Rebecca Tinsley in Rush County, Indiana. The couple married there in the 1830s. The researcher sent me the marriage record of Thomas Newman and Polly Tinsley who also married there in the 1830s, telling me that often times people used nicknames and that since the last names matched it was the same couple.
Being young and inexperienced (I was probably 14 at the time), I believed her.
Later I found out that Thomas and Polly were a separate couple, but the researcher was close. Thomas was William's brother and Polly was Rebecca's sister.
Remember in genealogy sometimes "close" isn't close enough.