I am a 16 year old boy studying in XI and i have a sister 14year old in IX and we are studying in the same?

school and i she good looking and i now as we have become ually matured i felt my freedom overtaken and the guys studying in my cl may be thinking of relation or having it with my sister(i don't know surely but i thought so) and due to this i m not able to study properly in XI plz tell what should i do