The only CD I have of his { Blues From The Delta on Vanguard } doesn't show any missing fingers in the photo and doesn't mention anything about it in the liner noted. Also no mention of being John Hurts brother in law. That's certainly doesn't answer your question but it's all I could find.

I'll bet someone over at the "woodshed" message board at www.guitarvideos.com would know for sure. You might try there too.