Board Thread:Manga/@comment-29919227-20160909220906/@comment-27441457-20160909221318

If Zeke IS Grisha's son, the only explanation I can think of is Grisha getting Ymir'd at some point before Keith found him. If he was stuck in a mindless Titan form for several years, his son could easily match him in age appearance after a while. Hopefully Grisha's journals will explain it next chapter, sooner rather than later.