Who's side are you on?

when i was younger my cousin would try and sexualy malest my sister she had somone looking out for her so he stopped and moved on to me but hwe would abuse me not only rape. im 16 he is 22. this happened up until i was 12. we moved. and since thoughs years i never told my parents its been mine and my sisters secret accept for the ocasional best friend or boyfriend we told. just recently she has been talking about telling our parents. i dont want her to. it happened so long ago and i dont want to cause drama or a huge fight within our family plus i guess im ashamed of it i dont want anyone to no but my sister wants everyone to no just how much of a pig he is. i guess its her revenge but i dont need revenge carma already got him he has never had a gf he works at wal-mart still lives at home wiht his parents has 1 friend is a total greaser so i dont think we should tell what do think we should do?