Can I give a younger sibling POV?
My brother is six years older than me. And from the earliest I can remember he would always hit/kick etc for no reason, or mainly because I wouldn't do what he said
His favourite line was 'respect your elders' 
I appreciate those who had younger siblings and you felt you were treated differently, but how would you like to be constantly bullied in your own home? I used to be so frightened by him.
The worst attack I can remember was one Saturday afternoon/evening when I was about 12, so he would of been about 18.
I was sat on a neighbours wall with my friend (the neighbours knew us and didn't mind) and my brother pulled up in a taxi and got out. He was drunk as he had been out drinking quite early on.
He saw me and my friend sat on the wall, and red mist descended. He started going bat shit, all because I was sat there
He went to grab me, but I managed to run and I got inside my house. He cornered me in the kitchen. My mum had managed to get in between us as he was throwing punches. She eventually managed to get him off and I ran out of the house. My dad was at work and never saw it. Funnily Dad was never there when he went off on one.
That night I refused to go home. I stayed at my friends house (it's only 3 doors away).
His behaviour was never dealt with, I never got an apology and the abuse continued until I left home at sixteen.
After I had left, my brother turned his anger onto my parents. He would regularly threaten my dad. Now after all these years (11 since I left) they admit I was right and it should of been dealt with years ago.
My mums Dsis saw the behaviour in my brother years ago (she raised three boys who even now wouldn't cross her
)and told my mum it needs sorting now. But as usual she buried her head in the sand
Now op, you are in better place to deal with this. Just because he is her sibling does not justify being tolerant. Ask yourself, if another child was doing this would you let it continue? HE IS ABUSING YOUR DD. IT HAS TO STOP.
He will only get worse if you don't. Please protect your DD.
Anyway the damage is now done. I won't forget what he's done. I'm civil and once my parents are no longer here then I do not want anything to do with him. I can almost forgive the behaviour when he was younger, but certainly not when he was an adult