Leaving the Nest

At some point in the 5 year time jump between Seasons 1 and 2 of Young Justice 5 year time jump, 18 year old Dick Grayson took on Nightwing identity, with 15 year old Tim Drake as a new 3rd Robin, unsure of himself. The cancellation of the show means we are unlikely to be told just how this happened. This is a fan's attempt to fill in the blanks.