Alex Wayne is the son of Bruce Wayne
and Vicki Vale
He was born sometime between the events of World's Finest and Batman Triumphant. He was named after his mother's friend, Alexander Knox.
Batman Triumphant (2000)
He is 15 in this this movie. He becomes the new Robin after Dick Grayson quits.
Batman Beyond (2019)
He gets posessed by the ghost of The Joker