Quote Originally Posted by zbonks
how can red xiii have kids if he was the only one left of his species?
On his deathbed, Bugenhagen obliquely suggests that Red XIII may not be the last member of his species.

Bugenhagen: It's a wide world and you must go out and see it... You may even find your life's mate. You never know.
The obvious implication, then, is that Red XIII did find his "life's mate."