I am glad you connected with family. Your parents long to talk to you but the stupid cult rules stand in their way. They apply rules to your sister that they wish they could apply to you. Were it me, I would reach out occasionally by inviting them to life events, sending photos of life events when they didn't attend, continually reaching out to the rest of the family.
Let the JW part of the family look bad on their own. Don't defend your parents, but remind family that it is the stupid cult rules that makes them that way. "Just try to forgive them. As screwed up as it is, I would welcome them back into my life if they put aside the JW rules." That's what I would say.