Could I get a refresher on how the kids were born? With the machine thing that made all the babies and time slime. Somewhere along the line I got all Confused and thought John and Jake were clones of each other for some reason

The machine gathered genetic material from Nanna, Grandpa, Mom Lalonde, and Bro Strider.

It made a clone of those four.  It also mixed the dna of grandpa and nanna to make John and Jade and mixed the dna of Mom and Bro to make Rose and Dave.

Time Portals then sent all the babies to various points in time. The scratch changed what times the babies were sent to thus in the Alpha kid timeline the Beta kids’ alternate selves became the old people and the Beta guardians’ alternate selves were the kids.

Hope that helps.