Board Thread:Manga/@comment-212.219.90.172-20160420133616/@comment-24930713-20160420201857

GodKingReiss wrote: If you're referring to the Ackermans who moved into the forests at the south of Wall Maria, that was referring to the Ackermans that Mikasa's father was born into, not Levi. Kuchel stayed in the Underground beneath Mitras and Wall Sina, so Levi would've been born there. He didn't leave the Underground until Erwin brought him into the Survey Corps.

To add to that, the spinoff, which was confirmed as canon in the later chapters of the Attack on Titan manga, make it very clear that it is extremely difficult to gain passage to the surface world; even for a day. And that most, if not all, people down their are poor and suffering from some sort of health problem from living down there. Making it even less likely that Levi could afford to go to the surface. It's also hinted at in the manga that Kenny not only abandoned him down there after teaching him everything he knew, but that he's never once visited him or helped him in anyway since.