how do you treat your brother or sister?

Treat them like you want to be treated yourself. I know they can be a pain in the butt, but siblings are a very special thing. Sometimes, it's ok to tell them go away! Just make sure you take the time to cultivate good relationships with them too. They obviously want to be like you and be with you, so be a good example to them and show them how to be better friends and people. It will make you better too, and you will be thankful for it in a few years. I hated my sister growing up, but now we are much closer. She saw what I did, and many of her choices would have been different if I had been a better model for her.