My sister was the golden child of the family. Once she was born, I was pretty much ignored. She was cuter, more charismatic, more cheerful and more extroverted and more eager to please.
Whereas I was not any of those things. I was contrary, irascible, not cute, and more than happy to argue adults into vitriolic anger and very averse to pleasing anyone. In most ways, I was actually content to be overlooked and ignored. I am naturally an introvert and was this way from a very young age. I believe my early experiences of being the unfavored child and then bullied for years amplified this tendency, but it was already pretty dang strong congenitally before any of that occurred.
As I said, I mostly was happy to be ignored. People not paying attention to me allowed me to do what I wanted to do and that was better than the alternative.
Mainly, though, I just hated being saddled with the responsibility for taking care of and watching my sister constantly while I received all the derision and blame for both anything she did wrong or that I did wrong. And all the while, people gleefully praised her for the most minor accomplishment while not even acknowledging that I did things like score at a 12.9 grade level (the highest possible grade level) in all subjects on a state-wide standardized test when I was in fourth fucking grade1. (My dad: “Must have been some kind of fluke.” Readers, it was not a fluke.)
That was not cool.