Rob and Khloe's exes were hanging together at the iGo.Live app launch event. Tyga was there too, but opted out of the reunion pic.
Chyna started dating Rob shortly after Lamar's near-fatal overdose. Lamar and Khloe had called it quits long before that so it's unclear how often BC and LO have crossed paths before.
Rob and Lamar were once BFFs. We're guessing Chyna couldn't pass on the shot at her ex photo op.