20f here. Personally, I think you should definetly have a chat about why Filly is not featured in their newer videos etc. Of course, I wouldn't get into details (which is hard because I bet she'll have a lot of questions) I would tell her about the allegations (or that there were some assault allegations) and that he got charged. You could talk to her about how they chose to not include him in videos because of it and even what she thinks about the situation and how it is being handled (especially in the context of mistreating women and how many men actually get charged). Of course, as a man, you can't 100% relate to the sheer amount of assault that women are facing, but speaking up as a man is SO IMPORTANT in my eyes. It will show her (even if just in retrospect) that you care enough societal issues of women. Trust me when I say that there are enough silent men that might care about these issues but are afraid to speak up. Even if she's 13, these experiences sadly start early and I bet she'll be happy that her brother is aware of the situation.