Dear jaybee,
Welcome to the board.
I am so sorry for what you are going thru, I can just hear the desperation in your voice. I am married to a BP husband and I can tell you that I completely understand what you and your family are dealing with. There are many on here who suffer with BP who can give you good insight on what an intervention might or might not do. Unfortunately, when someone is manic or depressed, many times they are difficult to reach, especially if they are not on meds to help! With my husband, he was in total denial 4 yrs ago when he was dx, he was truly unreachable and thought everyone else had the problem but himself. We went thru periods of time where he would treat me the worst and I was his biggest supporter. I just know that if your brother is not thinking rationally at the moment, an intervention might not produce the result you are hoping for.
One note of advice, it's easy to feel broken down by a person suffering with BP. The nightmare seems neverending and those taking care of or worrying about the BP one end up drained, upset, frustrated, or depressed themselves. Try to remember that this is an illness, and not your brother's true character. Many of the things he is doing are irrational, and he is going to have a hard time realizing that when he is not medicated or getting the help he needs.
I am sure you will receive some insightful feedback from many on here, all who understand and have been thru the same situations on both ends.
It may help to see a good psychotherapist as well, for yourself to cope, maybe even for your mother, and to ask them what the best route would be to help your brother. The denial is common, but unfortunately if he doesn't receive the treatment he needs soon, the illness can worsen.
Please keep posting, we're all here to help!!
Best Regards,
4support