AT WHAT POINT DO YOU SEVER YOUR LOYALTY TO A MENTALLY UNSOUND FAMILY MEMBER IF YOU FEEL YOUR LEAVING WOULD MAKE THEM HURT THEM SELVES?

When the pain of them staying involved in your life out weighs the pain of them not being in your life anymore. Also, you cutting the family member out of your life wouldn't be your fault because the family member has more issues then you severing them from your life. If this family member is mentally unsound and could hurt themself you could get them involuntary committed for a 72 hour mental health observation.. Let law enforcement or some mental health agency and let them know your family member is mentall and unsound and has threatened to harm their self.

Why does it have to be all or none? (i.e. you don't necessarily have to sever your relationship but if it is wearing YOU down, just reduce your contact)

If you do actually want to have absolutely zero contact with this person, do it slowly and gradually so there is less trauma.

P.S. - Why are you shouting? It seems a little sensitivity is in order here.

Hard to say so far I haven't encountered anyone in my family in that condition, depends on your degree of loyalty amongst other things I guess

There comes a time when one must...and I repeat must....cross that thresh-hold. It's a matter of personal sanity and one's own mental health. One must be responsible for one's own self first when it comes down to the bottom of the barrel...

When they start typing in Caps

when it becomes a detriment to your own family. ie spouse and children

I never could Debs,that is the time they need you most my good friend.

send them to the psych ward before you leave

Now.