Regardless age children need to know what is acceptable and what is just not allowed at home as long as they remain under the same roof.
Setting healthy and clear boundaries and limits, implementing them with total consistency, no exceptions and modeling the very behaviors we want them to show is the way to go.
If one is resistant to it, we need always to make adjustments to avoid manipulation or weakened rules which compensations have been exhausted and do not work any longer. Children, even less adolescents are not stupid, they do know very well what they want and need. So using the knowledge we have as parents of such preferences, needs and wishes, we could fairly control their behaviors, not in a mechanical but in assertive ways. They need to learn from it how to be respectful, responsible and unselfish.
If the unhealthy behaviors persist regardless the consequences implemented in consistent ways, then professional support would be necessary. Serious and friendly dialogue with them, to find out what could be bothering, frustrating or making feel uncomfortable at home or school would be necessary in order to be understanding and supportive. People, even more young ones, do act out their feelings, and nobody better than sibling to get some relief in the wrong ways.
Please feel free to share more if expecting further insight on this issue.
I would like to help with your question.
It would be helpful if you were to describe the inappropriate behaviors so that the answer you receive is better tailored to what is really happening. Teens are all about pushing boundaries and exploring. Perhaps that may be what is occurring in your family. It is hard to say without knowing more.
If you would like to provide some specific examples or a bit more information, I would be happy to reply.