Board Thread:Theories/@comment-33543289-20180703025502/@comment-33543289-20180704235126

The shifters could have been upgraded as seen with the Jaws Titan and the Beast as both posses hardening abilites (The Jaws because Ymir did not posses the hardening ability). Also Annie could very well be an illegitimate child like Historia was. As for the Braun serum. Maybe one of Reiner's relatives was a possesser of the Armored Titan at one point. But i see what you mean.