Hormones and my little brother's possible transition.
Hello. I am a married straight male 28 (cis?) and my little brother lives with me. He's going through a rough time and lived with my abusive mother for a lot longer than I did. I joined the military and got discharged last year. Since jan this year he's been living with me. I love him to death and we play LOL all the time. He and I have a TTRPG group and he likes to play as female characters. I don't mind if he enjoys girls, boys, or anything in between. I encourage him constantly to open up whenever he's ready and all he's told me is that he's unsure about his sexual orientation and that he thinks he likes girls. Recently, he's purchased what he described is estrogen and I'm concerned for his health and future development.
He's 23, a virgin, and hates leaving the house for pretty much any reason. I may be overreaching but I feel that his decision is a bit drastic. I want to support him fully but I'm worried he may regret this later in life. I had no idea I liked museums or would ever get married until recently. Lastly, I was a 68W (medic) and I do not like the idea of him using medicine without a provider's input. I'm a bit undereducated in any current gender studies and I have no idea how to navigate his possible transition. I know it's his choice but I want him to be happy for the rest of his life and I'm nervous he's possibly going in the wrong direction.
Please let me know your thoughts and insight so I can better educate myself. Thank you in advanced and let me know if I'm just a over protective brother.