Hi Blakegood88!

Thank you for explaining to me, you did write she did not exist in the current one, but I did not catch on, sorry about that. OK, so now I have better understanding on how you think. The way I see it you did have a twin sister who tragically did not get to survive birth, who you never got to know, and her room never got to be her room. Twins share a unique close connection and if one falls out like that I understand you have the feelings you have.
You have had a good childhood as you tend to wish to go back to it, but knowing you can't relive it as you, you reach for the twin sister's life. Your question is still complex. In my view there is already an alternative you living in an alternative reality,
I'm wondering too if it is possible for your spirit to take on the twin sister's life in that alternative, given that her spirit is not occupying the body, or decide to leave the body, or stay with the body
(and then it makes two of you in that body, a walk in, if that's possible?). I can relate to you wanting to re live the "same life" as another gender, but maybe you already do that. I got some strange visions in a dream from an ex where it looked as if my daughter was my son in that alternative reality if we would have stayed together,
given most likely if a string of other choices would have been made, that in our reality wasn't. If that is true, then it is then possible,
I guess, for your other you to be a girl, your twin sister, in the alternative reality, and your twin sister, if then surviving, being your twin brother.

Blessings