I’ll take a deep breath here and tap into my inner girl.
First thing, you didn’t say how Bro got in touch with you. Just contacting you is sign of a problem. You’ve blocked him, you’ve made it perfectly clear you don’t want to hear from him, and here he is violating your boundaries. Worse, unless there’s some innocent explanation I’m not thinking of, it’s downright creepy that he’s gone to the trouble of figuring out how to get around your block. Bro is bullying and stalking you. He’s bullying Hubby too, by making you miserable.
As an honorary girl, I would tell Hubby it’s time we decided between ourselves what we’re going to do about Bro, and put up a united front. Well, the united front will be Hubby, and you can relax in his shadow, because he’s going to make sure Bro will never bother you again.
I would tell Hubby that you’ve been trying to stay out from in between them, but that’s not your job. You and Hubby need to take care of each other; your priority as a couple needs to be keeping Bro out from between you two.
You didn’t say how Bro is trying to mess with your marriage. I’m guessing you’re not talking about his “stroke”. You mention that he talks to Hubby sometimes? If he’s badmouthing you to Hubby, make that the second item of business when you sit down to talk about stopping Bro’s bullying. Make sure you and Hubby are on the same side, you both know that Bro is fill of broshit, and Hubby isn’t going to take anything Bro says seriously, and you’re his wife, so he’s going to take everything you say seriously.
Now, you mentioned drugs. So we must have some compassion for Bro. He’s having a really hard time in his life. That doesn’t mean his abuse is ok, and it doesn’t mean you have to take his abuse. It just means, once Hubby helps you to be safe from Bro, you can feel the same toward him as you would if he weren’t bullying you; you could see that he’s a victim of his circumstances, and think of him more like a kid who can’t control himself than someone who is just mean.
It’s not your job to be Bro’s punching bag, or to take abuse on behalf of your husband. It’s not anyone’s job to take abuse, but definitely not yours. Clear the air with your man, make sure you’re on the same side and following the same action plan.
Try to get Bro some help, if you can. Maybe you’ve already done that. Drugs really suck. Peace to all three of you.