What is my legal obligation to continue care for my 100 year old mother and alcoholic brother who is abusive (verbally and physically)?

Get out today before you lose your nerve. Call Adult Protective Services, explain the situation and tell them mom is not safe from bro's outbursts.

Don't be surprised if they do nothing because mom and bro are competent. Do not call APS to ask result of the visit. Detach! Find a therapist that specializes in codependency.

First off, if he ever shows violence against you again, call law enforcement immediately. Next, stop going there and call APS, walk away from them, you have no responsibility towards either of them.

There are several books on Amazon that you can read about Codependency, get yourself a couple and it might not hurt to get one on boundaries too.

Stand up and take your life back, no one has the right to abuse you, this has gone far enough. No is a complete sentence, use it, a small two letter word that can change your life...for the better.

Your sisters have shown you what to do by walking away. Join the procession and live the life you want, not the lives of your brother and mother. You are late coming to this realization....but not too late for your rescue of yourself.

When your brother hit you, did you call the police to report? Now you may think, well what are they going to do? First, it starts a paper trail documenting abuse.  This can save a lot of time and grief later on. You have gone way beyond any "duty" you might have, so now you must care for yourself. You matter!! You say both mother and brother are competent - this means, IMO, you can just walk away. You have no POA, guardianship, etc. matters to negotiate. You can just walk.  I'm thinking that neither brother nor mother can cope SO how about calling cops for a wellness check, once you are clear of the situation? I would think that APS would then get involved, at which time you explain that you do not live there, you have no POA responsibilities and you will not assume daily responsibility. APS will have to turn to the state to get guardianship. You will have the police report to back up your refusal to accept abuse, should not be needed.I think you have more than fulfilled any moral duty you have and in fact, getting brother and mom into the state's control would be beneficial to both of them.  You might not think so, but if you go on, and breakdown, then what happens to them.  Do yourself and mom and brother a favor and bow out.  JoAnn has a good suggestion: food in the house, meds available.

Call APS and tell them ur brother is now hitting you. You will not put up with the abuse any longer. You need to take care of you and ur husband. That u are walking away and leaving ur brother to care for Mom. They may want to evaluate the situation and see what services are available to them.

Before u leave, make sure there is food available. Moms meds in a pill planner for the week. The place tidied up. That way you can't be accused of neglect. If ur brother hits u again, call the police.

Yes, call the county and ask for adult protection.  Tell them that your mom cannot take care of herself and you are not longer able to

If your brother and your mother are both mentally competent, you have no legal responsibility whatsoever towards them.

File a situation report with APS and walk away.

Do you think you will actually be able to do that, though? Twenty years is a long time to persist with such a situation, there must have been something that compelled you, no?

They are, as you said, mentally competent. That means you have ZERO obligation to them. Simply move away, as you would were you moving four states away from them. They may then avail themselves of such services as they require. As you said, your sisters walked away. They are, I assume, not in jail at this point.

Wow, the both of them have some nerve, don't they? To treat you like such a worthless person after you do so much for them for two decades. Disgusting. You've gotten great advice here; hopefully you can really walk away and not look back. Don't be surprised, however, if you get a call soon begging you to come back to help and maybe even apologizing for all the terrible behaviors. They need you, after all, so what will they do without you? Let THEM figure it out! Make a decision and don't back down. You've done more than enough for 2 people who don't deserve another minute of your attention

Wishing you the best of luck moving on with your OWN life now!

Your only obligation is to yourself and husband. No legal obligation to mother and brother. I agree with the others. Call APS and report the situation then walk away. Take care of you.