Nanna knew everything.
That is actually Nanna(pre-scratch Jane) and Grandpa(pre-scratch Jake) she is talking about. Their DNA was used to make John and Jade, who are very important to taking down the Condesce and Lord English, since they are uber-powerful gods right now.
I just love how Hussie reveals his hand before it happens, but you would never know until you’ve already seen it. Genius.
Also I’m using this to say that Jane/Jake is canon.