Don’t allow it. Explain it to them like this. When they are adults and in a relationship with another person, would it be okay to be unkind to that other person? No, it wouldn’t. It’s not okay to be mean to people we love.

Sibling stuff has many layers, but kindness is expected in a family. So if it’s mean, don’t allow it.

Just let it happen. My older sibling was cruel to me and my mom supported it. I no longer speak to either. That is your fate if you don’t get it under control.

Are you allowing the youngest to bother the oldest? Do you usually treat the youngest better? Do you have higher expectations for the oldest?

How old?

Give us examples. I have been accused of this. I am quick with words and was the older sibling. We can see if you are justified or being over sensitive.

Calling a little sister a B is not okay. Being a little sharp witted and sarcastic might be the kid’s personality and your aren’t going to change that.

I think my line for something like a sharp tongue would actually depend a bit on the temperament of the younger. Is she fine with it, shrugging it off? Then I wouldn't intervene unless it got out of hand, or anything physical.

If the younger is sensitive, I'd call it out as mean and stop it. And if I was accused of "favoring" I'd say "no one in this house is allowed to speak like that to anyone else. You or your sister."

Just pick your rules. Our rule is no name calling and if someone says stop you stop. Then I enforce those rules regardless of who is the offender.

I would tell the older DD that I'd never let the younger one talk to her that way, but she holds her tongue so there's no need to admonish the younger for something they don't do.

If anything said was not kind, I would step in. Siblings bicker and siblings tease, but truly being hurtful and unkind is where I draw the line. Also…I love you both very much, and it is not okay for you to treat your sibling this way. I wouldn’t be okay with them treating you this way, and I am not okay with you being unkind to them either.

Is this banter or verbal attacks?

When do you step in? Older DD has a very sharp tongue but if I speak up too much I get accused of preferring the younger DD. How to decide which comments/tones to let go and which to address?