When I first started dating my now-wife, our families didn't really understand what our futures would hold. There was stigma around whether we could have a 'normal' life and if people would accept us. I think we all go through uncertainty like this, whether you are in the LGBTQ+ community or not; it is second nature for humans to question and have doubts.
People don't need to understand others' choices or preferences; they just need to respect the individual and their right to make those choices. Whether you like brunettes, a certain gender, a sense of humor, or anything else about a person, you shouldn't have to explain why to anyone.
I'm happy to say that both my wife and I's families don't worry anymore and accept us as we are. I even think that my parents like her more than me! In the 15+ years that we have been together, our society has grown to be more accepting of all people. There is still a long way to go, and prejudice will never completely disappear, but I hope that the generations to follow, including our son's, will prove that love is love and that it is the most powerful thing in the world.