We use the names of people on documents as clues. Sometimes the reason why a person is listed on a document is fairly obvious, parents on a birth certificate for example.
But a witness on a deed or a will. The witness may be a relative, friend, or another warm body.
But the witness had to be of legal age and that may be a clue.
And always learn why names are on records and in what capacity they are acting. What requirements were there to act in that capacity?