I assume your parents believed you about the stepbrother doing this?
I think they probably don't feel they are in a position to listen to your complaints that he should not be living in the same house as yourself. Either there is a situation with his mother that they are not enlightening you about or something else is going on. It's too bad because you feel invaded. But possibly one thing to keep in mind that might help is that he could have been trying to do that for reasons that don't have to do with him being a little perv and peeping Tom as much as possibly wanting to show off to his buddies. (They might be filming their female relatives, for example.) That doesn't make it better, but it might keep you from being frightened of him.
Anyway, I'd make plans to move out. By that I mean, move in with a friend during summer vacations, or move out to college and don't come back. It's possible to go to school full time, summer and all. You would finish faster than many, and you could get a job and an apartment after that. If your parents disagree with this, tell them it is because you do not feel comfortable with your stepbrother in the same house any more. They can hardly argue that you don't have a reason.
So just to be clear, there was one incident a year ago and has anything at all happened since then?
I'm actually quite surprised this doesn't happen a lot more often - and maybe it does - with the constant access to recording equipment that young teens have.
Since you don't believe he will do anything else, I think it's time to put this in the past.
Its normal, what your step brother did is normal. Especially at his age. He's not your real brother, if He was He probably wouldn't have done it. If I had a really hott step sister I would probably be straight forward with Her if I Liked Her. Instead of what He did. He definitely needs to grow up, and You should really get used to guys doing stupid stuff like that, alot of guys are really immature and stupid. I'm 23 so I usually don't do stupid stuff like that at all. But there was a time when I was young and didn't know better, you should really move on and just get a mature and responsible boyfriend that truly loves you so your step brother doesn't do anything like that ever again.
Hi, You should maybe find him a nice girlfriend, also Maybe play some Ed Sheeran songs for him. If your daughter is good looking what He did is pretty common except for maybe a ten year old. I'm 23 and I would never do anything like that at this age, I usually go out to have some drinks and talk to people. That's where I usually make friends and meet girls. I'm sorry for what your dealing with hopefully He grows out of it.