How to reject someone?

A boy from my tution proposed to me on instagram. My best friend had already told me that the boy likes me. I didn't give him attention. Its my nature to answer everyone. So when he asked me ques on insta , I just replied to him. Then he said that he loves me. I told him that I don't want to be in a relationship. I even told him the reason that it is because I can't break my parents trust. I called him brother. But he doesn't get it that I dont like him. Now too he messaged me again. I don't want to hurt anyone so I told him politely but now its irritating me. What should I do now?
How to reject someone?
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