My prediction supports the fact that Cera's mother was around temporarily, but died later.
It all points to LBT 5. We all know that the Great Valley residents had to leave due to all the food being eaten by swarming leaf gobblers. (Man, those bugs sure had an appetite. Bigger than Spike's.) I believe that during the trip that some of the residents didn't survive. One of which was unfortunately Cera's mother. (Starvation, dehydration or get killed by a sharptooth? I don't know!)
Also, I believe that during LBT 5, one of Cera's elder siblings found someone, fell in love and mated. I predict the eggs containing Dinah and Dana were laid after LBT 5, and LBT 6 was sometime after they hatched.
I also believe that Cera's sibling didn't want the eggs at first. They didn't want to take care of them, and left the responsibility to Topsy while they got their bearings together. Obviously, they did get everything together after LBT 6 and took care of those twins. They're probably somewhere further away in the valley.
That's my prediction in a nutshell. It might not work, but it's the best I can come up with.
Hope this helps.
