I wish I didn't look up that username on reddit. This person is a 27 year old MTF transperson and is not the biological parent of this kid. Here's one of his recent posts:

I've been working with a group of mostly teens/young adults, many finding themselves not accepted by their parents and struggling to find themselves. I'll spare the bummer details, but one person in the group has been coming to me a lot of the love, support, and advice that their family just... refuses to give.

They finally have the chance to strike out on their own, but feel stuck, and dependant on their family. But well... I offered my home as something as a midpoint, show that they have other options. Things have escalated from there and...

They called me mom.

And I'm... adopting them.

So, he convinced a kid to leave home and move in with him and now they're both referring to themselves as "it". Am I reading this right? This is grooming behavior.