Really need more information than this.
It's really hard to make comments without knowing more. Is he working or in college? My son was unhappy living at home past 18 and so we helped him to go to the dorm at the local university. He needed to be around others his own age, and build his life and extended family. After getting his BA , he then took a Construction Engineering course, and is just finishing this up now (he's 28) He's a very responsible and well adapted guy. Some need to make their own way in the world so they don't regress into the terrible twos. More info might help here.