I went through that with an ex. His mom found out a horrible secret about his dad, kicked him out and promptly had a nervous breakdown. She went to live with his sister and he and his brother were supposed to take care of his mom’s house since break-ins at vacant properties are a common problem. His brother lived quite close, while we lived across the city, but my ex ended up shouldering the bulk of the responsibility.

I talked to my ex and he discussed it with his brother. His brother would promise to help, but then nearly always had an excuse to get out of it - meeting at his son’s school, working late, you name it. In the end, I think he maybe went there two times over the course of six months. He was earning more than my ex, but gave less money to help out his sister with their mom’s care using his kid as an excuse as well.

I completely understand how frustrating it can be. Sadly, there wasn’t much else I could do but try to discuss it with my ex. We couldn’t physically force him to do anything, much like with your BIL. His brother is the youngest and was always babied growing up. Unfortunately, people like that often never seem to grow up and don't change unless they want to. So sorry you are dealing with this.