First of all, you’re a damn good brother for wanting to help. Here’s my blunt advice, from someone who stuttered badly for 20+ years, then found a unique way to overcome my stutter and live a near fluent lifestyle. 1) You can’t do it for him. Your brother has to have a burning desire to beat his stutter. If he doesn’t, he won’t. 2) It takes daily practice, for the rest of his life. I practice every single day. (What I practice is nothing like what is taught in speech therapy) 3) Daily positivity and encouragement is required to fuel the overcoming of stuttering. There’s too much hardship involved not to have a steady diet of positivity. I’m giving you the straight truth from someone whose been where he is. I hope you consider following it.