All I can tell you is the truth.

Some people will be fine with it, some won't. You need to be willing to accept either possibility before you tell anyone. Tell him only as much as you are comfortable with. Just get to know him for now. As things start arising that it seems appropriate to mention something about it, tell him the bits you are comfortable with and if he asks more questions, answer them. Let the friendship progress naturally in this way. That way you don't push him away unnecessarily nor do you put yourself in an uncomfortable situation.