Was it rape if I was silent?

I've never told anyone about this. I'm the type of person that will bottle something up and never speak of it again.. I'm sorry this is so long, I just want to get it off my chest.... When I was 12 I was staying the night at my grandmas house and my older cousin showed up. He was 15 at the time. He had a troubled past and it was normal for him to just show up at my grandmas so I didn't think anything of it. I put my pjs on (a tank top and shorts) and was watching tv on the couch. He came and sat next to me while we were watching Catwoman. Then he moved closer and started cupping my breast and fondling it. I froze, I didn't say anything. I wasn't sure what was happening. He stopped and I moved to the opposite side of the couch. He then went and got a big comforter and put it over me then went to his side of the couch and covered himself.. I'm sitting there with my legs curled up trying to watch the movie when I feel him trying to put his foot between my legs. I tried to stay curled up but he managed to get his foot through and then I felt it.. He jammed his toe inside me. I once again froze; very confused as to why this was happening. I never said stop or no, I just froze. I've never told anyone about this because I'm afraid they'll say it wasn't a big deal since I didn't say stop or no. To this day, it is very awkward when I see him and I try not to be around him. Here's my problem. His sister is my absolute best friend, I've never told her.. And she's always trying to bail him out of trouble and always calling every couple of weeks to make sure he's ok and doing ok in rehab. I think she notices that I'm very reserved when she brings him up and realizes that I don't want to have anything to do with him. Like she wanted me to ride with her to go see him in rehab a couple hours away but I quickly changed the subject and she never brought it up again. Should I tell her? She's the only one I've considered telling however, she's very protective of him so I'm just afraid what she'll say. I refuse to tell my SO because he is a police officer and I don't want to hear anything legal, I'm just looking for support.