There is no way to disown the parents by children or children by parents, even though you see in newspapers regularly advertisements showing about this disowning thing. You publish an advertiesement and send a copy of the same to your parent saying that you disowned him. Even after that, he makes a will bequeating property, you need not take that property. If you don't take that property, somebody will usurp it or if no one claims, it goes to government.
My suggestion is if parents really give any property, and if you don't want to take it, give it to some orphanage and there orphans can get benefited.