Young Dick Grayson was adopted by Bruce Wayne after his circus performer parents were killed by criminals, Dick became Batman's sidekick, Robin. After an argument with Bruce, Dick left Gotham City for Blüdhaven, where he became Nightwing. He eventually returned to Gotham City and became an ally of Batman once again.
In LEGO Batman 2: DC Super Heroes, Robin's alter ego is named "Dick Grayson" as a mistake. However, at this point in the continuity, Dick is Nightwing. According to LEGO.com, Robin is Tim Drake in LEGO Batman 2, as Robin's civillian identity is shown as Tim Drake in the game. However, they updated the website to say Dick Grayson to match the game.