My cousin brother who is of age 14 proposed me. I love him in sibling way. But he really love me mad. What will I do?

My cousin brother confessed me in midnight. I told him to give me time. The next day I honestly told him that I love him as a brother. Since that day he was depressed and cold, rude to me. I couldn't watch him in this state. He is one of the most important person in life whom I can't let go. I didn't thought of myself and did a lyric prank on him of "crazy over you" by Blackpink and proposed him for his happiness. He became extremely overjoyed. Then I realized that this relationship was fake for me. I felt that even my career path is blocked by my parents and the love life is blocked too. I broke up with him. I got really rude and mean treatment from him from that day. He began to bully me. Then to make him stop doing that to me I pretended to be my sister and tell him that I got possessed and all. But he confessed again. I again told him I love him as brother. He became very bad coming in his friend's advice. I again had to propose him. He accepted it. Then I again made HIM broke up with me by texting as ghost to him to stay far from me. But things didn't went as planned. He told me about ghost thing and I didn't had a way out. So I ended it up by telling him that ghost won't let us be together unless we both become something in our life. I hope that his teenage crush on me would be ended after 10-15 years. But I still have doubt as one thing is for sure that he truly loves me and will not let go of me. Give advice to remove him without breaking his heart and him again loving me as a sister. Keep in mind that all confession, break-ups, the ghost and sister chat happened through texts. Don't hate me for the for doing all this. He was telling that he will suicide if we break up. He doesn't believe the fact that love doesn't hurts but loving the wrong person hurts. He thinks true love only come ones and I'm his true love. I want him to leave but at same time want him to stay. I don't understand my life!!!
My cousin brother who is of age 14 proposed me. I love him in sibling way. But he really love me mad. What will I do?
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