I dont think the oldest and the youngest should live together at all, but from experience I can tell you a 15 year old hookin is not from a stable home at all. I've never done it, but I had friends that did in their teen years and all of them had homes that were dysfunctional.
I'm not saying that all abused become abuser, but in IMO I cannot hold the same standard for adults for teens. I was a bad teen. I came from a single parent home and I wasnt abused or anything.
I had a good life, but I was bad and headstrong. I never did anything like this 15 year old did, but I did my fair share. Fights, gang violence, stealing, drug dealing, dating MUCH older men, etc I could go on, but my mom never, ever gave up on me. I liked to hurt people cause I was hurting. I was teased as a kid, low self esteem. Yes, I choose to do bad things, but I also choose to quit. I just grew up and out. I've seen my friends in jail and die or both.
So yeah I work with troubled teens cause someone has to. I have a degree, married and live a very normal life. My husband teases me about my past, but I am so happy just to be here.
I put no stock into the so called statistics and psychologist. I have been to many a shrink and think that most of the "treatment" they suggested for me was full of it. Yeah, we have an idea how the human brain works, but I think there is so much more we don't understand about how human beings think and abuse. Everyday some new theory is purposed. Its a guidline, but not really a rule I adhere to.