Question

So me and my family got on the topic of being transgender...I'm transgender but haven't told my family...they are Christian and very supportive of me being gay...I was trying to explain what being transgender means and my step mom made the comment that she didn't understand why people can't just be the way God made them...the comment hit me hard, but I didn't say anything and didnt try to explain anything further...they weren't being rude or mean or anything like that, but what would be some suggestions on how to answer this question