I don't believe in "shunning" familiy members just to give them a taste of their own medecine. However, I agree with JanH in that just because we are related to a person biologically does not mean we have to associate with them. Sometimes, especially if a person's family is still in the cult, they have very damaging patterns of behavior that can continue to do some serious harm to members of their family, whether they are in the truth or out.
In my family, my Mother continues to throw out mental triggers related to the brainwashing I experienced within the cult, such as : "Just wait for the new system, everything will be solved then." While in the past, these may have disturbed my well being, they no longer have an effect on me because I have ceased to believe them.