I know from a spoiler that the author gave in an interview that in the finale there’s a person (possibly Eren or Mikasa) not certain because it's giving it's back and it's holding a baby. So I was desperately hoping for it to be Eren and Mikasa's baby but with this chapter they're scaring me into thinking it could be Eren and Historia's.
No they are not. They belong to the same clan but they are not close related, I mean as far as we know the members of Levi's family all had black hair but Mikasa's dad that was the Ackerman one, was blonde. And they never hint at being blood related even when explaining their past or the Ackerman bloodline
There is better translation (2 versions) and quality at readsnk site, I highly recommand it, specially the "raw" one. :)
Also, I don't see a reason to think that Eren is a father of Historia's child. I read three translations so far and he just tells her that she should run or fight and she proposes that maybe instead of both she'd just get pregnant.
Also, I am SO GLAD that it's not going to be some obvious code-geass-ending. I love where this is going now. Although it'll be super depressing. But good and hq :)