Drums have a halal and haram usage. The haram usage is when it is used in entertainment gatherings. The halal usage is when they are used for certain Ashura processions. But in the past, they were mainly used for haram entertainment. If your brother needs the drum for treatment, then that’s fine.
The angels do not enter a house that has a drum if the drum is used for haram entertainment. Secondly, angels not entering such a house could also mean that it’s makrouh to keep it in the room, not that it’s haram.