On one hand I agree that you shouldn't put a religion/faith over family. On the other, they are wrong to disown you simply over what you choose to believe in. If it's not harming anyone, what's the big deal? But I guess it also depends how close you are to your family. If they've never really been there for you then I understand.
If are under 18, or still depend on your family, I would say no. If you are older than yes, if they are willing to disown you just for changing religion, then they are not real family. Family love each other no matter what.