So I'm going to try colate all the rumors regarding DCCU's history into chronological order..
Aged 8-11 ish his parents are murdered outside the Monarch Theatre under a train bridge.
Trains extensively for years in various martial arts, criminology etc...
Becomes Batman around aged 28-30..
Takes in Dick Grayson who's parents are murdered and he becomes Robin.
Grayson leaves and becomes Nightwing in Bludhaven.
Jason Todd becomes the 2nd Robin.
Todd is murdered by the Joker. Joker is locked up in Arkham Asylum along with Harley Quinn. Quinn is later moved to Belle Reve and inducted into the Suicide Squad.
Bruce retires as Batman.
Man of Steel Events.
Bruce comes out of retirement to deal with the potential threat of "Superman" aged around 42.