Not not all of them get Unicorn at Teen and it depends on which parent is the dominat parent the dominat parent determines what egg you get. I think if you mix a Unicorn an Helephant you have a 50% chance to get one or the other same with mixing with a Nightmare.
I just mixed a Dragon with 72 Pedigree and the Spritely skill with a Nightmare of 60 Pedigree an I ended up with a Nightmare with a 70 Pedigree score and the Spritely talent that it got at Ancient.
