My husband and I are renting a house and he went to jail for 6 months, so his brother and girlfriend moved in to help me with rent etc. but they have invaded my privace by stealing my mailbox key and taking my husbands license and bankcard out of my purse.
I want them to leave. Do I need to evict them if they fight me on this?

Yes, you have allowed them to establish residency and they must be evicted if they don't leave on their own accord. You can speed things along a bit by telling the autorities about the license and the card company about the fraud, tell the cops about the card fraud too.

Normally I would say you have to evict them. However, if they have stole from you, report it to the police. In this case, they may help you get them out.

But if they have paid anything towards the rent etc. its likely they will be considered a tenant and need to be formally evicted.