It is not common for a Koala to bear twins, and regrettably in this instance the Mum was struck and killed by a passing car. Fortunately, the driver stopped, and took the mother to the local vet, not knowing she was dead,  - where it was discovered she had these twins in her pouch.  

First photo: Tiny koala being fed with syringe ... sooo tiny!!
Followed by a pictorial chronology of their growth ...