I had a different spin put on this yesterday. I'll change all the names.
DD9 (4th grade) came home and was telling me about her day. She mentioned a boy named "Matt." She said Matt wanted to be a girl.

I asked how she knew that. Had he said....
I wish I was a girl.
You're lucky you're a girl.
I want to be a girl.
Those could mean different things. She said, "He says he wants to be a girl all the time. He ties his shirt up in back. (knotted above the waist of his pants) Sometimes, Joe says it too, but it's mainly Matt." After she illustrated the tied up shirt, the mental picture said it all. She went on to let me know her friend, Emma, had a crush on Matt, but he did not return it.

With as straight a face as I could muster, I told her Emma might want to move on to having a crush on a different boy since Matt did not feel the same about her.
At least I can handle this one. We had a family friend (born male, now lives as a woman....although I have no idea if thee sex change ever happened) who was a few years older than I was, and so "a boy who wants to be a girl" was a fact of life for our family. I figure I'll leave this topic alone since Matt may just be going through a stage, but if it turns out Matt is like my family friend, at least I'm on familiar ground. With our friend, it was not a stage. My mother said from the time he was a toddler, you knew he was different. But back in the 60s, they just didn't quite know what "the difference" was.
Birds and bees, I expected. My male friend wants to be a girl sort of surprised me.