Koko, I can understand why seeing a sibling copying after you might be annoying, but at some point, you have to stop caring what other people do and just focus on you. So your sibling believes (or is pretending to believe) as you do? Be yourself and be confident in yourself and don't worry about the credit for who came up with the belief system. People will like you for you and with either like or dislike your sibling on their own terms.