Any advice for coming out?

I am still in the closet and i’m scared of coming out. So far… The only one who knows who I am going to come out about it is my best friend and my little brother… My friend is really supportive of me but my brother absolutely refuses to even register me being trans and insists that I’m his older sister and that’s who I am now so that’s who ill always be….. Any advice for coming out…?