Did you relative get the wrong name in their head? I wrote a complete blog post about a man named Joseph Watson, only to refer to him as James Watson almost every time I used his name. Is it possible that your ancestor simply referred to the wrong person when giving information?
And proofread what you write–more than once. It’s possible that you made a mistake as well–and those accidental, “got it in my head wrong” mistakes sometimes come back to haunt you.