Improving relationship w lil bro

Just to provide a little context on my family relationship and dynamics: I have 3 siblings. 2 older brothers and a younger brother. My younger brother has a different father from the rest of us and we have a 13y age gap. I just turned 21.

I am naturally a pretty reserved and introverted person, so I don’t open up to people easily and unfortunately, do not have a close relationship with my stepfather. (We also don’t have much opportunities to interact due to drastically different schedules) On the other hand, I have a very close bond w my two older brothers as we all grew up together with them being the father figures in my life. I also only have an age difference of 1-2y from them.

My older brothers and I grew up in an environment that required us to mature quickly and become responsible for ourselves and minor household chores at a very young age. We didn’t have a great relationship with our dad or any other relatives really. Our ties with that side of the family was pretty much completely cut off when we were young. We were also struggling financially and did not have much as my mom was a single mother. My little brother was born at a time when our situation improved greatly and my mom decided to raise him through gentle parenting. I wouldn’t say that we are extremely financially well off now, but I do consider him as privileged. He is currently 8yo, has his own ipad, phone and laptop. He has boxes (and i mean BOXES) of toys that he would beg to buy only to play w it once and not touch ever again.

I understand completely that our different situations will lead to an obvious difference in our upbringings. And because of our large age gap, I am aware that our interests and mindset are likely to not match. It also means that our time schedules are different in the sense that I’m usually at work or college. (Don’t spend as much time together like I did w my older brothers) That doesn’t mean that I dislike him in any way whatsoever. In fact, I was practically the primary babysitter from when he was an infant to his toddler years. However, as he grew older, there’s an increasingly obvious wall between us.

I’ve noticed that in the little time that we do spend together, I will often reprimand him for his rude behavior or attitude towards my mom. I understand that he is still a child, but I don’t wish for him to grow up with a privileged and spoiled mindset. I often find him saying incredibly insensitive remarks not only about sensitive topics, but also to our mom. He is ALWAYS talking back to us, especially when we are talking to him about his behavior. It will usually end w him saying stuff like “I don’t understand. You don’t know English.” (my mother’s first language isn’t english, but she tries to communicate w it as much as possible) That is only a small example of his behavior at home. Often times, I will be the one confronting and trying to correct him when he does such things. This results in us always getting into arguments or banters.

My mother and brothers are unwilling to engage in such conversations with my younger brother and will often ask for it to be dropped. They say that they understand that his behavior is an issue, but that the way I go about it isn’t right. They’ve mentioned that I’m always criticizing him and it seems like I dislike him.

Don’t get me wrong. He’s a very smart kid and has always been interested in history and landmarks since he was a toddler. I don’t expect him to understand broad and major world concepts. I just wish that he has basic respect and manners. I don’t want to project my childhood onto him, and I definitely don’t want our relationship to be strained. I’m at a loss and not sure how to go about this to improve our relationship. I’m trying my best.

And just to clarify, I don’t hate him. I love him a lot. My family means the absolute world to me.