I’m not sure how to respond. I know I was not my parents’ favorite child, simply because I was not a clone of my older sister. My parents made no bones about it when talking to me or about me, and they managed to cultivate a narcissistic sociopath (in all seriousness) who I eventually had to break contact with because she’s so toxic. I’m so glad my own children enjoy each other.
Be encouraged that at least you and your brother have a decent relationship, and if he says he’s happy, that’s terrific. Your mother is losing out on the enjoyment of knowing both of her children are doing well, despite her perceptions of what success may be. It truly is her loss.