I have two aurleons, both different gender and I tried to have them breed. They did not pop up as either male or female option. I realized both were adolescent. When do they grow up to be adolescent? (They are both roughly 2 days old)

When their maturity reaches a value of 648 - or 27 days * 24 hours. This amount of time starts when an Eggling is first created, so if it's a caught or generated pet it will start at a maturity much higher than 0.

Atm, you can only see maturity values if the pet is tested and if you look at its image URL.