Depends if Ackerman is just a group name or if it's a family name. A lot of people think it's just a group, though I wonder how Mikasa's dad and Mikasa fit into it because they would have had to have been involved to get the name.
If it's a family name it's still to early to tell what the relation between Mikasa and Levi would be. Anything is possible. There are lots of similarities between them so it could be a really close blood relation, or they might have both been genetically enhanced. If Eren could become a titan with a serum, then I'm sure there was other sorts of experimentations going on.
I don't think their ages can tell us anything either. Levi is supposed to be older than Mikasa, but then again Ymir is supposed to be 60+ years old and she looks 16. Who is to say something like that isn't the case with Mikasa or her parents as well? Levi also looks much younger than he actually is which was on purpose according to Isayama. With all the weird stuff going on nothing is impossible.
Regarding that bandage on the wrist, I wouldn't put much thought into that. ACWNR is not related to the manga and Levi's wrist are never shown to have the same bandage as Mikasa ever again. It was just a thing for that cover. Plus the scar on Mikasa's wrist is from her mothers side of the family, so far it's only confirmed Levi would be on the fathers side... unless the relation between them is brother and sister.