I would suggest that you find out why he's there before you kick him out. To enter someone's dreams takes a great deal of energy and is rarely done carelessly. . .unless someone is young and stupid with the extra energy to waiste.
There are other times that someone is placed in shared dreams, because the intent of the universe has created a link between the two (or more) individuals. In which case you have to learn why your linked. The other person may be just as unhappy about it as you, or they may believe it's just a weird but normal dream (which he may not even remember).
If you're sure that he's deliberately "trespassing" then light a candle and will the link to be broken. It doesn't have to be complicated.
