finally coming to terms

Bonnie
So, when I was in the fourth grade my oldest brother moved away to college in another state, and that caused a change in my older brother to change. He became sexually curious, and what better way for him to explore than on his 10 year old little sister? 
It started off innocently enough, we would cuddle on the couch, I used to be very affectionate so I saw nothing wrong with it, but I quickly got worse. He began forcing himself upon me, kissing me, trying to finger me, and he tried to put his dick in me. This went on for nearly a year and every time he'd do this he'd bring a knife into the room and threaten me with it if I made a sound.
 I finally came to terms with it three years ago when I turned 18. That's when all the trauma really set in. I now suffer with severe chronic depression, severe anxiety, and PTSD. I am heavily medicated because I tried to take my own life several times. It really fucked me up.
But thankfully I have an amazing group of friends and boyfriend that fully understand and support me. My brother has been in and out of jail several times. We have also never told our parents.
Am I in the wrong for not telling them? If I were a parent I would want to know, but I also know that that would be something else added to their already full plates.