I'm so glad he has you looking out for him. The National Stuttering Association(NSA) has teen meet ups, but it depends on where you live. If you live in or near a major city, it is more likely there will be a teen chapter. The Open Stuttering channel on YouTube would be awesome for you/him to watch. If you are willing to put in the work and time, the National Stuttering Foundation has a free podcast made to educate professional speech therapists about stuttering. This isn't a rec for your brother but rather for yourself since the target audience is adult professionals. Some other organizations have online teen meet ups . . . can't remember the names . . . maybe Friends who Stutter? If he is open to it, they are either free or inexpensive and could really help. "Sometimes I Just Stutter" is a free, short ebook you can download from the National Stuttering Foundation. It is a book written from a child's perspective, maybe a little too young for your brother, but it can be pretty eye opening to what it is like growing up with a stutter and gives some dos and don'ts for communicating with a person who stutters. BTW, anxiety doesn't cause stuttering. People who stutter stutter even when they aren't feeling nervous, but anxiety can make it worse.