There's something i have said for a long time about being trans when someone asks about it. I tell them to "imagine that tomorrow you wake up in the body of the opposite sex, but absolutely nothing else about you has changed. Wouldn't you desperately want to get back into the correct body? Now imagine feeling that every day of your entire life."
Whether you use it in a calm friendly way, or an angry hostile way, it always gives people something to think on. And usually they begin to understand more than they had thought of.
I'm just glad you have an open minded family, as not all of us are so lucky.