Board Thread:General Discussion/@comment-11016223-20130904052318/@comment-24463671-20140125211542

They are humonid-turtles. Seeing what the mutagen can do they could have easily ended up like Justin or Timmothy, but they probably got the humanoid part from Splinter before the mutation.

But enough with the science, just because Karai and Splinter are not biologically related to the Turtles does NOT mean their not family.