Oneshot plotbunny that didn't go away. I don't own Batman, but here's one thing I might do with it if I did...
Damian hadn't really thought getting Colin adopted would be this easy. He should have told Stephanie the situation sooner. Upon calmly and rationally explaining Colin in general to Ms. Brown, the woman was all-but ready to drive to St. Aiden's and take him in. Damian could see where Stephanie got her do-good nature from, as it certainly couldn't be from her father Cluemaster. What he couldn't see was what sorts of things getting Colin adopted would cause:
1—Damian was now in public school. Alfred and Dick had convinced his father that he would behave himself if there was any chance some "incident" he was in could cause Colin issues with their peers. They were correct, and Damian slightly loathed them for it.
2—It became traditional for Abuse and Batgirl to end patrols with waffles with their mom. The inclusion of Robin and Oracle was optional, the inclusion of Red Robin was not advised after the first try.
3—Upon first meeting Colin, Jason was reduced to a stuttering wreck, before accusing Bruce and Dick of something that made Scarlet facepalm. Damian decided it had something to do with both having red hair and he and Colin invited Scarlet to play Mario Kart with them. Jason flipped again when he found out Colin's codename was 'Abuse.' He too was banned from waffle-time.
4—Ms. Brown was only slightly surprised to find a large storage closet in her basement converted to a mini-batcave after Damian and Colin's summer break. She was more surprised to find out that Damian had somehow rewired the entire house to save energy, including the mini-cave.
5—When Dick left town for extended periods, Ms. Brown knew Damian would temporarily move in. That was why she bought Colin a bunk bed, after all.
6—Assassins thinking Damian was less protected in the Brown house met a poor reception thanks to Stephanie's tricks, Damian's speed, Colin's strength, and Ms. Brown's frying pan. Damian saved the security video for posterity.
7—Ms. Brown decided to go work at Leslie Thomson's clinic, and was surprised to find a reformed supervillain working there as a guard. Colin and Stephanie decided to put extra surveillance on the Cavalier (aka Mortimer Drake) in case he started trying to date their mom.
8—Hush was found to be Colin's father through a bizarre series of events involving Harley Quinn, the Calculator, and evil slinkies, and was subsequently so terrified by Ms. Brown that he committed himself to Arkham instantly. Colin and Stephanie proceeded to rant about supervillain fathers and Damian added anecdotes about supervillain grandfathers.
9—When the Cluemaster escaped again his new stepson took more than a little glee in introducing him to Abuse's brass knuckles.
10—Barbara, Jason, Stephanie, and Ms. Brown were not happy to find that Damian, Colin, and Scarlet—aka Sasha—had been training Nell behind their backs. Alfred scolded them soundly and then asked what size clothes he needed to reinforce with Kevlar.
11—Talia attempting to coerce her son back to her side was rudely derailed by his friends coming over for movie night. Damian made her sit through every film while he "contemplated" her offer, too. She finally left when they pulled out Kung Fu Panda 2.
12—By middle school, the Red Hood was back with the Batfamily, sidekick included, and all four kids shared a lunch table. Sasha often made fun of Damian's clothes, and he retaliated by mocking her hair. Colin and Nell simply took notes in case they needed future blackmail.
13—When Damian and Colin were found kissing, no one really was surprised. Sasha lip-locking with Chris Kent was only a bit more odd, really, though Jason wanted kryptonite access. Then Nell announced she was dating Irey West and everyone in the cave went into shock that was only ceased when Tim realized Nell didn't have a secret identity and everyone focused on that instead.
It was a fun family, in the end.