My boyfriend's sister likes his ex better than me?

My boyfriend and I are dating for over a year now, but we were best friends for years before we started dating. The problem is his sister always makes me feel that she like the ex better...and a huger problem is that the ex still wants my boyfriend and doing everything she can so just she can be close to my boyfriend again...I'm so sad..I've been doing the best to reach out his sister.
My boyfriend's sister likes his ex better than me?
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