I'm thinking of disowning my family
Leaving a family is harsh. Why would you disown the people you love?
They always make bad jokes about me.
It is wrong to be made fun of. You should not just cut out your family members but confront them and tell them how you feel.
I will miss them. I will disown them for good.
Fight fire with fire. You can always have your own bad jokes as a comeback. They will probably stop if your start making your own bad jokes.