Wouldn't becoming a criminal for the sake of revenge just **** up OP's own life more?
I would think exposing them both to the entire extended family would be way better.
The neighbors always talk, too. There would be nowhere they can go without the shame following them. Shame is very powerful when spread wide enough, no matter how stupid a person is.

I would expose them both, disown the entire family and move out. Nothing says "worst parents in the world" quite like cutting them out of your life, and no matter what they say the message is clear to the entire family, no one will believe their excuses. I have cut some family members out and it was the best, healthiest thing I've ever done. ^-^