I feel like I should at least testify here to the potentiality for long-term trauma in a situation like this--In my case, though, the exposure was to my parents' emotionally/sexually coercive and abusive dynamic with each other, and I was exposed, for years, to their loud, awful sexual activity.
We shared a wall, not a bed thankfully, but it didn't much matter: it was as if the whole house was breaking, aggressive, daily (always at night but sometimes in broad daylight as well--sometimes with their door cracked opened, sometimes not, but either way I was not permitted to sleep with my door closed and besides the wall that separated us was paper thin).
I was so afraid to ask them to stop, to tell them that it hurt, scared, and confused me, that I would hide in my room--enduring the exposure--rather than leave and draw attention to myself, humiliate them, or expose them (though this was of course backwards as they demonstrated no concern for me and exposed themselves constantly). I was, at this poster's age, privy to my father's coercive efforts, waking my other up from sleep for sex, sulking or getting angry in order to have sex, all of it. I did not come close to having the assertiveness of the poster (I wish); I just behaved like a prisoner in the situation.
There are more awful details and other events I'll leave out, and surely parents are authority figures in ways a sibling isn't (and an abuse dynamic between my parents/towards my mother is for certain a factor in traumatizing me), but I can assure you this exposure functions now through disturbing auditory memories. At the end of the day, there is no room for my parents, given my physical proximity to them and age back then (this went on from age 12-22, when I finally moved out for good), to not have known or anticipated or imagined that I would be exposed to their behavior; it's hard for me to find ways to think about their decision-making process that are compassionate towards them.
The best I can do is to conclude that they were so deeply involved in their own abusive dynamic that they could not think of me as a person being impacted by the inevitable exposure to it all. It makes me wonder if the poster's sister was involved in an abusive relationship that drove her behavior.
I'm 40 now, have problems in my own sex life--triggers, intrusive thoughts or memories, feelings of repulsion, my body turning off or touch being painful or at least repulsive--that I have tried to deny for many years on the grounds that "exposure" doesn't count as "abuse". But I'm here and it does. (And two therapists have told me I have PTSD...though as an adolescent I would never have known).
