I have toddler who is just under 2.5 y/o and is constantly hurting and being mean to his baby brother who is 9 months old. He will often take toys away from his brother just because his brother is holding them. Sometimes he pushes his brother over while he's sitting up, or kicks him while they're sitting together to keep him away from any nearby toys.
I think at least part of his behavior is rooted in jealousy. We make sure to give the toddler a lot of love and attention, but as soon we give any attention to the baby, he starts to act up more.
We have explained to him that it's not nice to take toys or push and that he should say sorry whenever he does it. We remind him to apologize and return the toy after it happens, and he does, but the behavior continues. We try especially hard to praise him for being nice whenever he plays nicely with his brother. I thought this would work, but it's almost like an immediate knee-jerk reaction for him to just be mean whenever he feels emotional. He just can't help it. I feel like I must be doing something wrong. What else can I do to help my toddler understand this behavior is unacceptable and teach him to be nice?
Update to answer question in the comments:
The toddler does seem to actually like his brother most of the time. He gets excited when the baby wakes up from naps and loves to sing "good morning to you" to him. They also play well together in the bath and he likes giving the baby high-fives and hugs and stuff like that. The mean behavior is not super common and seems more impulsive than anything. It's still concerning to me though because he's actually hurting his defenseless brother on a consistent basis.