I wouldn’t be so quick to pick out ones and twos of any disorder to try to place a label on anyone.
It is entirely possible that he feels the need to travel, explore and figure out what he is looking for.
There is an instinct in a lot of people that drives us to find a place where we feel “at home”, or a place that is thrilling, or somewhere that has opportunities for career.
The is doubly true if he is between 20 and 30.
Perfect example, after I left my parents’ home, I never lived anywhere for longer than 2 years. Whether I was moving across town, or to a different country.
Certainly doesn’t mean I have any sort of disorder.
For me personally, it was in persuit of the lifestyle and work that would satisfy my need for change, challenge and freedom.
So, maybe there is more to your brother’s story.
But travel, even if disappointing (as it often is), isn’t necessarily a problem. We all need to feel like we are comfortable, engaged, challenged and satisfied with our lifestyle.