Kylie Jenner and half-brother Rob Kardashian are on less than good terms following news he's been romantically linked to Blac Chyna.<br />"Kylie is livid," a source tells PEOPLE.<br />"She feels super betrayed and can't understand why someone in her own family would stab her in the back like that."<br />Blac Chyna, whose birth name is Angela Renée White, is Tyga's ex-fiancée, and together they have a son, King Cairo, 3.<br />On Monday, Blac Chyna shared an Instagram photo of herself wrapped in the tattooed arms of Kardashian, seemingly announcing her new relationship with Jenner's sibling.
