It sounds like many of us have had similiar experiences starting when we were about 4 or 5 and often involved with a big sis in playing dressup in mom's old clothing. That was how it began for me so thought I would share how much that it has helped having a big sis on my side as I go through this.
I remember my sis playing dressup and I didn't pay any attention at first. Then one night I had this dream I was a girl. How weird I remember thinking. Anyway for some reason I told my sis about the dream that was strange cuz then we weren't exactly friends. I was the little brother who when I got mad at her I would beat her up. She was older by 2 years but I was stronger and more aggressive. So anyway for reason I choose her to tell about my dream. I don't remember her saying anything but like probably how weird. But a few days later while my mom was at work and she was playing dressup. I happened to walk in the room and she asked me if I wanted to play too and I did. Well it went from there and soon it became our thing. It was beginning of us being best friends and my biggest supporter.
Of course we got caught one day, but it didn't stop us. eventually we got caught enough that my mom sat me down and had a good talk with me. That led to counseling and therapy and eventually learning I was Trans.
Long story short, when I was 13 I started blockers, let my hair grow and later hormones and 3 years ago went full time as girl.
All the way my sis was helping me. We graduated from mom's clothes to hers since we were close enough in size. I was never big as a guy, but had caught up in size with sis. when she got a new outfit she would let me try it on. as she learned about fashion so I did I. We would talk about everything together. When she started using makeup, she got me into that so I learned early about clothing fashion, how to apply makeup. I remember getting really jealous when she started developing and of course I didn't. But she would talk to me and later as our younger sis got old enough to me interested in this stuff, it was the 3 of us, but mostly her and me.
As I got older talk with my friends (boys then) began to change from just talking sports to about girls. When talking sports I was all in as that has been an interest and still is now I am a girl. But when the talk turned to girls I would listen, but never had much to say. My last year as a guy was in 8th grade. Guys would talk about wanting to start dating and stuff like that about girls. I never wanted to do what they talked about with a girl. I always wanted to be that girl they were talking about. So by then my big sis was in 10th grade and she was dating. So she would talk to be about what guys were saying abut girls cuz she was trying to figure out what guys were thinking. So I guess it was good for both of us. So of course, I was interested in what she would talk with girls and about guys. So I guess it was good for both of us.I remember her telling me about her dates, her first kiss, first time a guy felt her up and stuff. Then of course, the first time she did it with a guy.
So now I am full time as a girl and I am one of the girls talking about guys. So as my friends started dating and talking with us about it, I remember one time when a subject came that I knew nothing about, but all the others did. You might have guessed what that was. Yeah it was having periods. So they started talking about it and I had gone silent which was unusual for me and one of them asked how I was doing in handling it. I'm sure I probably turned red with embarassment, I managed to say something like OK and let it go at that. But that day when I got home from school, I went in my sis' room and told her about it. She liked closed the door and said we better talk cuz you are going to need to know about this stuff. So instead of the mother-daughter talk I got the big sis to little sis talk. I remember her saying that it is good that guys are clueless about girls periods and cycles cuz otherwise they might know when girls were easier to have ask sex with. She showed me her calendar that she marked what day period started and ended so she would always know where about she was in her cycle. So that was really really helpful cuz the subject has come come up again and I better understood what they were talking about and what I could say even though I wasn't really having periods of course.
So anyway, that's something about how much having this special relationship with my big sis has helped me learn and adjust to living as a girl.
You will see a lot of discussion here about Physical and Emotional transition, but I think the Social transition is equally as important. Your situation is a bit different as you started earlier than most. But for many of us, transition didn’t start until much later. We didn’t have the benefit of learning from mothers, sisters, aunts and grandmothers, so it’s like 0 to 60 over more like a matter of months. I think that is one of the most difficult things about transition because there is no medical fix for it and counseling won’t fix it either. It is just information that you have to learn and absorb however you can come by it. I think what you learned from your sister and hopefully continue to learn, is invaluable...