My teen nephews are staying with me and they are cheap as fuck. They hide soda and don't share things with anyone.
How do you feel about your family behaving like that?
I'm frustrated. I can't stand seeing my teen nephews be so cheap.
Family members are supposed to share things and help each other out and so it's understandable that you're so frustrated with the behavior of your teen nephews. They should know better and be more conscientious towards others. You might be able to get them to share more by sharing things yourself and emphasizing how good it is to share with others.
I'm going to punish them. It's not my fault that they are poor. They should not be so selfish.
I don't think it's right for you to punish them for not sharing, especially because they don't have much money. Punishing them for that might only make them resent you, which would lead to them being even less likely to share. I think you should show them how good it feels to share with others.