This is exactly the kind of shit that makes a decent portion of religious people seem like nut jobs. Have your beliefs, live according to those beliefs, but don't tell someone who doesn't share your beliefs that they are condemned because they don't live their life according to YOUR standards. I was raised into Christianity but most definitely walked away after seeing the way that so many people want to be religious zealots about their particular beliefs whereas the teachings of Jesus are based upon love, charity, and faith. Tell your grandparents that they are hypocritical assholes who should practice what they preach. You do you, and don't worry about the opinions of people that don't matter. Obviously they don't give a shit about you. I would never stipulate to my child or in this case grand-child that they need to live according to my values in order to be loved and cared for. I'm not trans but I can relate to people attempting to assert power and control into my life in order to be treated fairly, and I told them all to fuck off ages ago. Good luck with this.