Need to tell him that the financial support will end on xx/xx/xx - give him maybe 3 months. Let him rant and be mad. You have done far more than he had any right to expect. And tell him no, he doesn't have a job, he has a hobby.
Are you the one that is supporting him or another family member?
If you are not the one supporting him, you really don't have a say in how that family member spends their money. Even if this is your sibling and you don't get as much as this person, it's none of your business how the money is spent.
- you can approach this person about the family member's mental illness. But if it's not bothering them or the person and the person is not harming others, there isn't much to do.
If you are supporting the person, cut them off.
If he were a part of my family I would give notice my last (or next) check is my last. I feel no obligation to support someone who doesn't face reality and habitually accepts handouts. If others in the family continue to support him that's OK, but I'll not be one of them.
Nothing can be done. If that's how he chooses to live his life, it's nobody else's business. If you don't like it you need to learn to deal with it.
You do have the responsibility to get the person help or at least try to. He is obviously sick. Contact social services in your area and see what can be done.