I'm sorry so many here have toxic relations with family/siblings. My story is a bit different - and a little long, sry.
I won't lie, I had looked back on my childhood often and wondered if I was "the golden child". Least until my senior year, I was getting academic achievement awards and made good grades. I avoided making mistakes and did everything my parents wanted me to (well, maybe a moment or two of rebellion) My little sis, in my view, got more discipline for things, but I pitied her and whenever I was rewarded, I would always consider her and try to offer compliments or secret rewards to show she mattered too. There was still some competition between us, but nothing really toxic.
As an adult, I realize this perceived "golden child syndrome" might not have been true. My little sis was more extroverted and learned things in life that I've fallen behind on because I thought I needed to be perfect. When I failed my first college semester, it finally sunk in that I'm not perfect. I just cared about academic success, so I really hadn't learned much. Also, because of me being autistic, I might have gotten more positive attention from my parents bc I was sensitive. And I still am.
Not to compare, but my sister, to me, has a more full life than I atm. She can drive, has a job she loves, and has a family of her own, all without a college degree and I am so proud of her! She's also insanely talented with art, music and writing, but she is not able to explore her talents because of real life, so I try to encourage her. Meanwhile, I'm living sorta in a bubble, being the autistic sensitive sister, but enjoying my artistic "talents" and improving on them, despite my boring, anxiety-ridden life.
Guess what I'm saying is, we have reasons to envy each other a little, but unlike most siblings, we understand each others flaws and see each other equally despite the four year age gap and an ASD diagnosis. I may be dealing with an inferiority complex bc of how I've looked at my life and compared it to my awesome little sister, but that's more my fault (not hers nor my parents - they did their best) and I'm working on myself and not competing with my sister. I still look up to her for life things, as she always looked up to me for creative things. That is something we will treasure about each other, no matter which directions our lives take.
Competition/envy can sometimes be beneficial - helps you takes steps to improve yourself if you do it the right way, like my sissy. But don't let it control your life. You gotta live a little separate from family, if you can. I'll get there eventually, just may need more time.
EDIT: I just read DasIsWunderblyst's post mentioning the "invisible sibling" and that sounds more like my issue rn cause I can't stand alot of attention (well, except online, I'm building up confidence, lol). Also can't resent my parents bc of morals/values as well. Idk. Parents are a different topic. Might get back into therapy on that one.