I know how you feel. I lost my mom when I was sixteen. She died of breast cancer. My parents didn't want my brother and I to worry since we were so young so they didn't tell us how bad it really was. When I got the news that she had died it was shocking. That was ten years ago and it is still tough at times. So while I didn't lose a sibling I can empathize with you because of the similar experience with my mom. Take care.