Jason and Dick look alike. They always have, the two boys looking remarkably like Bruce despite being adopted. Black hair, tan, blue eyes (at least before Jason dipped in the Lazarus pit, his are green now). Both tall, even if Jason’s taller. Both with a propensity to take women (and men) home. And Tim of course fits that’s same mold, a bit of player before settling down with Kon. And obviously Bruce, dark hair, blue eyes., the original ‘playboy’ of the family. So when a dark haired toddler is dropped off on the doorstep with a note, they can’t tell who’s kid it is. Must be one of theirs. Especially when the note says ‘He’s yours. Two. Can’t keep him.’