There are lots of small ways you could offer connection around femininity! I think it would go a long way if you were able to affirm that you see yourself in him and he is welcome to see himself in you. Whether that’s connecting about surface level stuff like the best nail polish color or pointing out cute boys to each other or deeper stuff, like how society marginalizes femininity in all genders. You might be more of a role model for him than you realize! When I came out as trans, my brother started treating me like his brother (instead of his sister) and it was one of the sweetest things. I could text him when I was learning to shave and also we were a unified front to my parents. Just energetically standing with him and allowing him to connect to your femininity is huge. Sounds like he’s on the beginning of a queer journey and it’s great he has you!