Well... since I was an only child who grew up with a quite elderly extended family I can't relate to the sibling rivalry aspect of this. However I can certainly relate to some of the other things you mentioned.

Had I been born a normal boy, I think I probably would have had pretty good parents. Unfortunately what my parents got was an anxiety-ridden, depressive tranny at a time when mental illness was something embarrassing to be feared, & the whole idea that a person could be transgender was pretty-much unheard of.

My parents never pressured me to be anything in particular. But I at least always felt there was an underlying assumption that I would turn out to be somebody. Sadly, however, I turned out to be a complete & utter failure at pretty-much everything I ever tried or did. Fortunately... my parents didn't live to witness some of my more blatant failures. Unfortunately… they didn't miss some of the worst of them either.

I'm now fast approaching 70 years old. And it's only now I think that I've finally reached a point where most of it (not all) just doesn't matter anymore. But I know, from personal experience, one can do themselves a lot of damage trying to live up to what they perceive other peoples' expectations to be. Sooner or later, I think, you just have to find a way to be the person you are... whoever that is. Chances are, in reality, that's primarily what your parents want for you too... just to be happy. I wish you well...