You should tell me at first you are a girl or a boy.
Why would you want to sleep naked. That is pretty weird to ask. Sleep naked in your own bed if you just must do so, but you should have pajamas on or at least some boxers or underwear. Who in the world sleeps in the bed with their 13 year old sibling? At that age you should be having your own bed.
If you wanted to have secs you can do that.
It is sorta weird...but I mean if you were wearing something it would be different but I personally would ask for a new bed.
Honestly I don't think that right! You need your own space to mature, however I understand you and your brother may be close, but I suggest wearing atleast underwear and pajamas, you're teenager that are going through puberty and developing, you need to have some pride and self respect, not to mention that you should have privacy!
Thats probably the most grossest thing I have ever heard in my entire life and I think that I need to go brush my teeth and take a cold shower