Good evening, I can relate to your situation, and I empathize with you.
I am not sure exactly what the text book definition is, however it can simply be called a negative influence.
How long has this been occurring?
I would suggest that you speak to the father of your daughter in regards XXXXX XXXXX he says about your son. What he might not understand is that the wedge that he may be causing (at least in your daughter's mind) between your daughter and her brother is damaging to the relationship, not only that she will develop with her brother, but in the future,it could affect her relationship with men as well. If I can help you in any other way, please let me know. I wish you the best!