I understand your annoyance. My friend is actually going through a similar situation. They keep telling him to go upstairs or go outside while they fuck eachother in the living room. Me and him found this very conflicting. Luckily he reached out to other family members and he got the help that he needed. In this instance, i think you and your sister should probably reach out to, Friends, Family. Heck, maybe even your therapist could help (if you have one). Above all else though. Know that you are not alone and there are people here that would take time out of there day to talk to you and cheer you up. I hope you have an amazing rest of your day, god bless you 🙌