Yonce's childhood vocal coach, David Lee Brewer, has written a tell-all book -- titled Beyoncé: Raising Genius: A Teacher and his Prodigy ...this book contains some deep stuff!!!

According to EurWeb, Brewer alleges that he saw drug use and infidelity on both Mathew and Tina's part, writing in an excerpt that Tina once pointed out that "Mathew's drug use had gotten out of hand." .

Want more info on the book check out this website.... David Lee Brewer Jr.'s website.