Currently there are only two female tree kangaroos living in Zoorasia; one is the 17-year-old 'Wali' in the photo, and the other is 7-year-old 'Tani', who arrived from Perth zoo in September 2013, but will be receiving a male very soon under the international breeding programme (I thought it was going to be this very month but I'm not sure). The male will be paired with Tani, so I guess the new male should be a young one.
Zoorasia-born 'Biwa', now 13 years old, was sent to Melbourne Zoo in 2013. She may not be exactly young, but both her parents were born in the wild so she is considered to be valuable.