You are the reincarnation of their mother that they loved dearly. Genya and Sanemi have never got along after what had happened that day, rest of siblings died and their mother was turned into a demon and Sanemi had to end up killing her when they were both kids, they were never on the same page after that and now here they are, Genya was trying to apologize and Sanemi wasn’t having it and yelled at him only for you and Tanjiro to come in and help but once Genya and Sanemi saw you, they froze.