Oh gosh, he is absolutely gorgeous. Poor sweet thing though being so scared like that.
Do you have him in a separate room or have you just let him loose in the house?

If he is loose, I think it would be best to put him in a room and let him adjust to his new surroundings in a more quiet manner and when he isn't so scared, then slowly introduce him to your other two.
Denyce gave some very good advice.