Don't they exist in a an alternate timeline? Think about it: Rip put the team together to stop Vandal Savage from taking over the world and stop his wife and kid's murder. Now the killed Vandal Savage and stopped him from taking over the world yet Rip's wife and son are still dead. So now they've created an alternate timeline in which Vandal Savage never took over the world and Rip's wife and kid are dead. So that would mean that Arrow takes place in an alternate timeline since both shows take place in the SAME timeline. So that means that in the original timeline Laurel Lance is still alive and is the Black Canary and she and Oliver are a couple. Why couldn't they set Arrow in the original timeline?