Kaitou Kid revealed

[mangaluva]

I doubt they're related. I think it'll be "WTF?!" a) because he looks so much like Shinichi and b) because he's far too young to have been stealing twenty years before. Although Shinichi may already have some suspicions about that.
Come to that, has Hakuba ever noticed that?

[Conia]

Long Lost Brother FTW‼‼

[Callid]

It has been asked if he would tell the police...
Well, Conan is very law-loyal (in this aspect he is like the Det. Boys). I think he would agonize over telling the police, and I'm not sure about his final decision. If KID agrees, he will most likely make a deal with him, ordering him to stop stealing. If KID tells him his reasons (his murdered father), he might even help him.
If KID denies the deal and does not tell him, I consider it most likely that Conan will turn him in. To let a thief escape would contradict his philosophy.
I think you could compare it with the case that Agasa is a murderer (I think it was a memory of Ran in the Night Baron case).