Anyone else have 2 under 2??

Our baby girl is almost 6 months and he loves her to death which I’m so grateful for, but he’s having a hard time understanding that she’s still to little to be super rough with. Tonight he accidentally kicked her but not hard enough to make her cry so I say him up checked on her and said buddy I know your tired we’re getting ready for bed but you almost really hurt sissy you need to be careful especially when you’re upset. But as soon as I said you hurt sissy he started screaming I know he’s a little sensitive but I didn’t think I said anything wrong to make him scream. I picked her up to check on her and she was fine. Is there something other than jealousy that I’m missing or is this just normal.