Rob Kardashian is popping back up in the most unexpected way - and it involves none other than his famously complicated ex, Blac Chyna! Yes, you read that right. The notoriously private Kardashian brother just did something fans almost never see: he gave his ex a very public nod on social media. And now, we're raising our eyebrows in the best way possible! Related: Blac Chyna Fires Back HARD At Ex-Boyfriend's Abuse Allegations! On Monday, Rob took to his rarely-used Instagram account to repost a video of Chyna showing off her hair and promoting a product from her Hearts Pure Cosmetics line.