Parenting, personalities, environments and age gaps.
Too many parents swear up and down that they raised their children the same but many don’t. People change as they age and due to different circumstances so the parents one sibling had isn’t necessarily the same another has.
Parents were both working parents and father was around more when I was growing up. When my mother was home, I rather she was at work. She was always quite negative and the first thing usually out of her mouth was a complaint or an order. I was constantly dismissed, called weak, a cow, too nice, selfish, too nonchalant, negative comments about my body, my facial features (different from hers), and many of the things I liked or enjoyed. By time, she was around more I was in secondary while my sister was in primary and it had only gotten worse.
My sister and I are 6/7 years apart. My mother heavily favours my sister and they are very much alike. Anyone could say something nice about me and she would be uncomfortable, but if it was my sister, she would agree and praise her. This also led to my sister joining in with my mother, getting away with more and knowing she would, and all around negative behaviour from her towards me to the point she would get me in trouble because she could. My father was usually in my corner pointing out that she treated me differently and then it would cause an argument, but with my sister and I, it was just sibling stuff and I’m the oldest so had to lead by example, yet when she would instigate an issue, we would both be told off instead of just her. I don’t think we became somewhat cordial until after I had my first child so 29, her 22/23.
We talk maybe 2 times a year despite my dad wanting us to talk more and trying for years (should be happy we are talking at all), but when it comes down to it, if we weren’t family, we would likely never have met and if we did, doubtful we would have been more than mere acquaintances if that.