Okaaay, I don’t get it. If the 7 daughters from SJ belong to Aku, why are they killed without the magic sword? Why can’t they shape-shift like Aku? 

I’m starting to think that the Mother was tricked into sleeping  with someone who pretended to be Aku and was like ‘Yeah, no, I’m totally Aku, let’s do it!’ but decided to take off when he found out she was having 7 kids. Made an excuse, something about Jack of course, and left and that was when she decided to use her kids to fight Jack.

And I’am pretty sure I know who the real dad would be if someone looked like Aku.

50 years later and he’s going around tricking people into believing he’s Aku so they would give him what he wants.