People with autism vary widely in their ability to communicate. Unfortunately, some are never able to communicate verbally. Options for children like your borther include using sign language, an augmentative communication device (rather like a small computer that can talk for him), or use of a picture based communication system like the Picture Exchange Communication System (PECS).
Statistically speaking, given your brother's age, it is unlikely that he will become a verbal communicator. I would highly recommend your family seek out speech therapy services for your brother (if he doesn't already receive them). His speech pathologist will be able to determine what kind of communication system would be right for him and would be able to give advice to your family on how you can help him communicate more effectively.