You love your schoolmate he's 18 but you asked him to be just your brother how can you start a conversation with him?

Smile and touch his elbow while you are talking about anything. Touching a man's elbow speaks directly to his genitals and says you are interested but not pushy. It will not make him love you-nothing can do that if the chemistry isn't there for him-but it will definitely show him that the door is open if he chooses to walk through.