Sister with a big butt

My little sister has always been my protected one, we've gotten along so well that whenever she had problems, she's always come to me. Imagine how many guys have tried to hit on her because of how pretty she is, but there's always been her older brother looking out for her. From now on, she'll no longer be my little sister and to me, she's already a full-fledged woman, especially after the mess she dumped on me