A similar position? No. But I do have some experience. I know it wasn't a simple mistake. Your brother's development had to have been screwed up and or impaired mental functioning at the time to molest a four year old at age 16. Screwed up development isn't his fault of course but the point is there were more factors to it. If you understand why it happened it may help you to work through it. So you should confront him; he probably won't have the answers your looking for but it'll help you regardless to just express your feelings. So work through your fear and confront him.
Per your parents it isn't about what good it does to them it's about what good it does to you. Quit making yourself suffer for other people's ignorance. I say ignorance because telling them dosn't mean it will hurt them dramatically. Yes it will shock and hurt but pain can be dealt with and worked through. Opening up, seeking help from them, may well bring you closer. The one thing I do suggest however is understanding why you feel like telling them will take a huge weight off your shoulders. And if you can take it off any other way then try it but if you can't then tell them. So long as you share the molestation as something that hurt you and is hurting you then it'll be good.(make sure you approach confronting your brother this way as well) If you start putting your brother down that's where chaos and drama get added in and where it will really hurt people. They may also be a good source of information for why it happened. Per your feelings of selfishness for telling them you could say it is selfish. But what your doing is telling someone your hurting and asking for help. It's not exactly healthy to consider that sort of thing selfish. Because then you don't seek help and don't try to work through your own pain which are both negative things. So selfish or not, asking people for help when you need it is the right thing to do.
If the child sexual abuse is having any other effects on you I hope your working through them and have talked to a counsellor. Best wishes.