She did establish the finders keepers rule. While plainly personal property isn't respected, this should be valid. However, with how the parents are, planning for that to blow up would be a good idea.

The parent's hypocrisy is amazing. I'm sorry. You're having to deal with this. Sadly the best advice I have is persevere in getting good grades and go to college and get a good career you can get a good job you can support yourself on and you'll have a good life. It will get better. I'm sorry you can't trust your family to not steal from you.