Your ex but now he is your step brother as your mother married his father. You didn't know he will be your step brother until you moved into his house and your careless parents left you with him in that house as they are on honeymoon. He is older than you and now is a businessman.
As you entered the house you came face to face with him. He was still on the couch sipping coffee and reading a book. He seemed to know about your existence but you were clueless about his. He looked up from his book and said in a authoritative voice
"Do I need to send you invitation to get inside the house?"
He didn't even bother to get a reply from you as he put down his cup ready to leave for the office.