Not sure if you know about it, but I just found on youtube one of J.T. IV's songs, in the comment section a user claims to be John's nephew-in-law. His channel doesn't look as an active one, but why don't try? I would like it, but I can't just because of my bad english. And if I made some errors while writing just let me know about it.
https://www.youtube.com/watch?v=uMxLWGrAFqg