What do you do in this kind of family situation?

You inherit a considerable amount of money, you share it equally between your family and keep a bigger portion. Your oldest sibling loses all their share by spending it on ridiculous things and is now living with your elderly parents making life much difficult for them, treating them badly and asking them for money and spending it on stupid things again. I hate the fact he's burdening our parents like he did when we were younger and at 30 they still baby him. What do I do?