Hello Huldra-fey -
Jinxing powder. Hopefully not in your shoe, though, right? it would probably jinx yourself. Furthermore, I'd feel inclined to try a vinegar jar for this situation, with statements such as: "your life will turn sour, unless you change your behaviour towards me" etc. Something like that. And I guess you could include the jinxing powder in it as well.
Though you did mention that it is harming your family. If this is about a non-productive, toxic behaviour someone close to you has nourished, you might want to take a look at the "cast off evil" line of products, as carried by the Lucky Mojo Co:
http://www.luckymojo.com/castoffevil.html instead of resorting to hexing and jinxing, you could use those on behalf of the aforementioned person. It might help in disengaging from bad habits, depending on what the situation is. This would qualify as a more gentle approach, which could seem more fitting if this is about someone you or your family members care about.
Good luck.