ANSWER:

You shouldn’t tell him any thing. 

Just warn your mother and sister that they will be kafir if they go to fortune tellers or people dealing with black magic.

QUESTION: I Asked You Question About My Mom And Sis Going To This Guy To Do Something About The Person Who’s Not Interested In Marrying My Sis Should I Warn That Person And His Family About This the Thing is They Also Do Biddah Would Probably Go And Get Taweez for Help If There In Bad Situation Because That’s How Normal It Is Here