I miss you, brother

After being forced into an orphanage due to their parents' unfortunate death. Billionaire Bruce Wayne adopts Dick. Unknowingly leaving Dick's younger brother behind. Upon returning to the orphanage, Danny is nowhere to be found.
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It had been five years since the fall and 17-year-old Dick Grayson-Wayne was frustrated. In the past five years, they had gotten close to no leads on where Danny could be. It had been around 2 years since their last lead had led them to a pitiful dead end and Dick was starting to lose hope.

However, when Vlad Masters invites Bruce for a friendly business dinner in his manor, the bats can't help but notice his sneaky glances at Dick.
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It's been 5 years since the fall. 3 years since he moved on, and 2 years since the portal incident, and Danny's 13-year-old life couldn't be more normal. If being a ghost-fighting superhero could be considered normal.

It had been a regular day. He fought a few ghosts, got 3 hours of sleep, woke up for school, and so on. What he didn't expect was to get a frantic call from the Fruitloop telling him to "come over immediately".

OR
Danny and Dick are long-lost siblings who reunite purely accidentally.