Since your daughters don't want his daughter around, your husband should tell them to pack their stuff and go live with their father.

**Raises hand**

I too grew up with a disturbed sibling. Hardbroke, violent, raging...for years, she beat the crap out of me (I was younger) and kept our household in a permanent state of chaos. My mother tried her best, but ultimately my sibling ended up a junkie, a thief, and incarcerated. As for me, the good kid? I got the hell out as soon as possible and kept a safe distance. My mother lost out on a closer, healthier relationship with me because she was obsessed with helping her bad kid.

Your DH should be able to remain in his daughter's life and get her the help she needs while still maintaining boundaries and basic standards of behavior for all of the children. Of course, some will cast stones and claim that he's putting his skids above his bios, but to quote Spock, " The needs of the many outweigh the needs of the few, or of the one." The truth is, every child deserves to live in peace,

To the OP--If your SD is indeed bipolar, she should be on meds to control that. If those meds don't work, she should be re-evaluated and try another type of medication.

The difference between bipolar manipulation and something like borderline is that the bipolar manipulation is done out of feeling like desperation--they go through their manic and depressive phases because of their chemical imbalance and it's in those highs and lows that they desperately try to make things "go their way" no matter the cost because they feel like it's "the only way".

However, for a personality disorder such as borderline or narcissism, the manipulation is a bit more subtle and planned out. Less unstable unless they are becoming unhinged.

I feel that at 12, her options should not have been exhausted just yet, and that she should be trying different types of meds to keep her symptoms under control. HOWEVER, I can say that meds for bipolar often turn patients into a shell of their former self, kind of wafting through the days like a ghost. It's a really sad situation.

As an older person I've unfortunately seen too many disturbed children (in intact homes with wonderful parents) just grow up to be utter pieces of sh*t. Yes one has to try with minor children, but no one should assume that with the proper "help" they can all be salvaged. Because all too many can't.

A friend has a daughter who was "different" literally from age 1. Turns out she is bi-polar. Her parents have spent HUNDREDS OF THOUSANDS OF DOLLARS sending her to every treatment program imaginable. No divorce, loving parents, other siblings are totally normal, this one was just born damaged. She's 40 and in prison now.

Bi-polar in some ways is like cancer. Some can be overcome - but some is not curable.

Another couple I know - father is grad of West Point and Harvard Business School, mother is educated and daughter of a professor. Two of the most loving decent people I've ever known. Their son who I've known all of his life is now in prison. The parents tried everything - nothing worked.

I could probably give another 50 examples of a child being a total ahole from birth.

I think sometimes that the mentally deranged teen in someways is like having an Ebola patient - you have to isolate them to protect the others in the home.