My older half-brother was a great annoyance throughout my childhood.
I was incredibly small for my age and he was always big for his age. He was also 6 years older than me.
He was never afraid to mock, pick on, tease, or belittle me.
Sometimes he would just grab me - in front of everyone - hold me on the floor and say "GET OUT" and I would have to squeem my way out of him. Everyone in the family would watch me fail and cry.
I remember I always had to 'act perfect' around him. If I ever did or said something he deemed incorrect he would immedaitely call me a retarded dumbass, and everyone would agree with him automatically.
He completely dominated me in all sports. Even as I got older he could win without trying.
The most brutal part - every month he would bring a new girl to the house. A few times I was forced to hear them fuck in the other room.
(All of this during his teenage years.)
He grew up to be 6'3 - me, 5'5.
I have seen plenty of examples of good older brothers. I have also seen many bad older brothers.
Some brothers will try to guide and help their younger brothers. Nutritionally, socially, and so on. I am pretty jealous of that. It's just more RNG.