They are right, there is a lethal factor with two velvets bred together, and two whites bred together. Females should NEVER be paird with a male until atleast 8 months - i'm waiting until around 1year or more to start putting them together. Sorry to say, but once you put a male and female together- you're breeding. When she comes into heat, they'll more than likely mate..I suggest reading through the other post, and learn about breeding before doing it. Also, where are your animals coming from? I have to suggest NOT using petstore animals, or animals of unknown histories, by breeding these animals, you're basically ruining everyones hard work to preserv the chinchilla strain.