My older brother came out... What can I do?

As the title says, my older brother came out as trans. We are 1 year apart, he's 23 and I am 22 yo. How did it came about? We were in the kitchen, joking around and I slapped his back and felt something. I asked him if he was wearing a bra as a joke and from that point he came out as trans. FYI, he came out as bisexual to me about 2-3 weeks ago so this came out of nowhere for me. Dont get me wrong, I am fully supportive myself and I don't doubt him at all. He was very supportive of me when I came out as bisexual years ago. We've talked and he decided that he will never come out to our Mom because she wouldn't accept me when I did so this for sure will put our Mom to the grave. We still love our Mom despite that fact. Its complicated.

Its still pretty new so he's still figuring things out and seeing what works for him. It definitely feels strange for me considering that we grew up super close and he's always been straight in my head but I guess I shouldn't have put that expectation considering that he never talked about his attraction to girls. He doesn't care which pronouns to use yet hence, the use of he/him.

I guess my question is, how or what can I do to support him more? I have non binary friends and fully support them but I guess the idea of having someone much closer in my life is totally different than just a friend. I want to make sure that I say the right things and doesn't offend him. I am happy that he is happy. I have a feeling that not much wouldn't change between us and I am just being paranoid because I dont want to scare him away.