Well done on getting away ninja. Hope you get time to breathe and think!
Just disengage. Use ANY means you can to continue to disengage and stay that way. Keep contact to a minimum. So she's now desperately trying emotional blackmail to get you to ENGAGE again? Don't. Don't make any reply to that. It's a disgusting thing to say, total blackmail - 'if you're not going to give me your money, I won't let you communicate with him'. She's really showing what a scumbag she is, isn't she? She doesn't have her son's best interests at heart, as we've now seen - that comment just proves it further. He could probably do with a chat with his sister just to know that you're worried about his health, to know you've been asking about him - it would probably do him good. As would him hearing from YOU why you think a bail-out is NOT the solution to this. But his mother is going to withold that from him, use him as a bargaining chip. Words don't cover it - all I can say is no matter what happens, never forget the way DBmum (is that P??) has acted here. This is who she is. Never trust this woman ever again.
I hope that over the weekend you get time to read all the comments here and I hope they strengthen your resolve. I won't re-hash, but there's one aspect that strikes me that I don't think has been touched on much.
If you did help out financially now (be that by selling your land OR taking on running the business) what you would be doing is letting them know once and for all that you are willing to continue to bail him out. It's quite a crucial point.
Right now, you are actually in a very strong position. Think about it - if you ask someone for a favour, the chances are they'll consider it and help if they can, unless there's a reason not to. You did this and more, helping your brother above and beyond any call of duty.
But if you ask someone for a favour, then let them down in return, the chances are that the next time you ask for a favour, the reply will be 'are you joking? Not a chance mate - look what happened last time!' Pretty logical. Most people would expect this reply. (Most defaulters wouldn't have the brass neck to ask again!)
This is where you are. Your DB and his mum are chancing their arm, totally, and they know it. What they are asking is breathtakingly ridiculous, criminally selfish and grasping. They know that any sensible person should laugh them out of town, saying 'Sorry, you made a fool of me once, I'd be a fool to give you a penny!' Their only chance is that they know you have a weak point, and they are absolutely going to bust a gut to put you under so much pressure, harrass you so vilely, that you become so distressed that you give in to them. (Horrid treatment of a family member, isn't it? Could you imagine doing that to your brother in return? Does that tell you something?)
Right now your DB mum probably expects that you will not give her the money. She is probably already casting around for other options. I repeat, you are in a strong position, the strongest you ever will be. His creditors won't wait for long. They need action NOW. You only have to remain out of contact 'utterly stressed, totally upset that they would hound you like this' for a short time, and the moment will have passed. You will be FREE of this dysfunctional family trap you're in.
But what happens if you cave?
You then become the fool. The person who can be bullied. The person who endlessly gives favours, makes conditions, but is so weak that the bullies know they won't stand up for themselves and impose them. If you give your brother ANYTHING this time round, you are setting up a pattern for the future, and you will effectively be stuffed. Because next time (and there will be a next time - 150K didn't stop this happening, did it?) they will KNOW that all they have to do is harrass you and harrass you until you give in. Look at the stress you're under now. Another thirty years of it cropping up periodically? It's just not worth thinking about.
So - DO IT NOW. Stop the cycle now. Because if you give in this time, trying to put your foot down next time will be twice as hard, if not impossible. Think to the future. This will never end. And next time (as you sit there with your ever growing mortgage, and the ugly house built right on your boundary that's sliced off a nice chunk of its value, and your ever-dwindling savings as you continue to be asked for 10K, and 25K, and a free bit of accountancy, and, and, and...) you will be sitting there wishing with all your heart that you had just been that little bit stronger.
Can you go on a proper holiday? Seriously, last minute two week break? I know it sounds drastic, but consider the above, and it's cheap at the price!
Happy weekend xx (in my old homeland! :) )