how can I get my little brother to stay off his phone?

for context, I'm 17m and my little brother 12m. he uses his phone all the time, when he's brushing his teeth, doing homework, in the bathroom. I think this is a very harmful habit for his age. my parents are no help, they also are all the time on their phone, and don't really care about my brother's addiction.

I'm looking to gradually get him to use his phone less. I don't want to just tell him to not use it when he's doing certain activities bc I know he won't listen.

how should I start? what should I do?