DD regularly makes negative comments about her sibling. Sometimes it's triggered by me saying something, like asking him not to pick up something dirty, she will say "yeah DS don't do that, it's dumb" or something similar. Other times he might annoy her and she criticises him in return. I end up telling her off a lot as she does it so often and I am worried it is affecting his self esteem! She seems aware of it at least partly, her new year's resolution was to be nicer to him! But it hasn't helped, it's like she's got into the habit and she does it without thinking. It's not really premeditated and she doesn't go out of her way to be mean to him but it's just a series of negative comments and observations throughout the day, not said in anger, just like normal conversation! I don't know how to stop it but I know it's not fair for DS to be treated like that. It's not only DS she says these kind of comments to, sometimes me too but its mostly directed at him. I am both worried about the effect of the comments on DS and also the effect on DD of me telling her off for it multiple times a day. I feel like she's always on his case and I then end up being always on hers.