Joint tenant wants out but remaining tenant to stay.?

I signed a rental agreement with my dad and his girlfriend and now I want out lest he start defaulting on his payments and make ME look bad on my credit. So my question is, to get off the agreement do I fill out a notice of intent to vacate the property to the landlord and if by doing that does my dad still get to stay on or does he get kicked out too? All I'd like to do is change the agreement so that it doesn't read me on the agreement anymore seeing as how I don't even live there. They've asked for a notarized doent stating that i no longer want to be on the agreement but isn't there a form I could fill out?