Unlocking young races

[DrIstvaan]

Hello All! I don't yet understand how one "unlocks" a young race to play. I read in some Steam discussion that you need to win a diplomatic/military victory while allied with one or more young races to unlock that race, but I see a certain young race unlocked even though I won the last sector with a Guild win.
Someone please explain when, exactly, a young race is unlocked.
EDIT: Upon further reading, I see that if a race "emerges", that should be enough as well, but it's also not clear what emerging entails, so some details would be welcome.
(If it's explained somewhere, then please excuse me for opening a new thread; I looked in the manual and did a search here but found no answer.)