I've been thinking about this and I just realized that Valkorian's son and daughter should be a lot younger than they are.
Think about it, the emperor disappeared at the end of SoR and the eternal fleet shows up at Marr's ship about a few months later. Then we are imprisoned for 5 years. So how did the emperor build the eternal fleet, raise a family of kids that are in their 20's and build all the infrastructure on Zakuul in a 6 year period?