Gekka created an entire race from herself (the Water), does that mean there may be more candidates among them? Or did she fool the test operator like Kyouka did for Chika?
Given that Gekka is thousands of years old and capable of some sort of pathenogensis, Enka might have her DNA not the other way around. In other words Enka is a lifeform derived or descended from Ocean or Gekka herself. Or actually was a form of Gekka herself when she was enraged by something.
How old is Enka? If Enka was thousands of years old when he died, he could easily have fathered children who were already hundreds or thousands of years old at the time of his death.