Something that's been bothering me recently:
EG (Chapter 5)
quote: "What are we supposed to do, then?" asked a boy, a really small black kid who had a top bunk near Ender's.
And then again:
quote: "It does to me." Dap picked up the nearest desk, which happened to belong to the boy who bunked above Ender. Dap read it, smiled very slightly, gave back the desk.
The 2nd one of those quotes is after Ender, Shen, Bernard, and Shafts get mentioned so if it was referring any of them it would have probably used their name.
A quote from the 1985 edition of EG (Chapter 6). Note: this was taken out in the 1991 "Author's definitive edition" for obvious reasons.
quote: They grinned. Then Ender said, "Better invite Bernard."
Alai cocked an eyebrow. "Oh?" "And Shen." "That little slanty-eyed butt-wiggler?" Ender decided that Alai was joking. "Hey, we can't all be niggers." Alai grinned. "My grandpa would've killed you for that." "My great great grandpa would have sold him first," "Let's go get Bernard and Shen and freeze these bugger-lovers."
Based off of that I would think that it might be referring to Alai. However, I don't remember any other references to Alai being black. Or to him being "really small". My memory of the Shadow series isn't the best, maybe more is said about him there?
One final quote that bears doubt on whether Alai could have had the bunk above Ender: EG (Chapter 7)
quote: When they got to the barracks. Ender squatted down by his bed and said, "Get your desk and bring it over here. I'll show you how." But when Alai brought his desk to Ender's bed, Ender was just sitting there, his lockers still closed.