Is it normal that parents don't see their son perfect? but they love a younger son more than older son's?

May 2020
we are three brothers. im the younger one the reason is -

my brother argued with my mother about the past what they did to them. my brother argued about money and study, they didn't favor them a thing. like buying them clothes and toys. I recorded their argument and I heard the record again. then it was confusing me.

so I told my dad about it and heard the record too. after that "I told my dad - what did you do to them?" "Why didn't you give them a favor?" he told me secretly - "I didn't see their good success" "I didn't like them" "I didn't see their good in inside" I feel really bad about it and doubtful. (which I think it was wrong thoughts about parenting decisions, but my dad denies it and lying about what they did to them like beating and abusing).

you wanna know something? when I was 8/9 we were in the market. I saw my dad brought my mom a cloth and only me. (i told my dad about the market in a few days ago and he was like a greedy face with looking up in the ceiling) they (parents) told in front of my brothers. mom did saying "It won’t fit their size" and then my brother felt bad on that day. I think it was criticizing.
I don't remember quietly ☹ this makes me more confused now I think my parents ruin their mental health without understanding them.

now my brothers are taking revenge towards them. my parents only love/likes me more than them. I don't think my parents are bad or something. I do remember my dad used to drink and smoke with his friends in the office.
can you pls fill me with enlightenment?