He doesn't belong in your parents' house. He's using your generosity as a means to facilitate his drug habit. You may not be doing him a favor by housing him. It sounds as though he needs to be admitted into an in-patient drug program. He may have health benefits from his current job that will pay some, if not most, of it. But whether he can afford it or not, that's where he needs to be. You can schedule an evaluation for him and if he doesn't go, you should kick him out immediately.

Don't give him money and if his parents decide to pay for treatment, they should pay the facility directly.

He might be upset about not seeing his daughter, but his daughter is better off without him unless and until he's clean.

Good luck.