Interesting. I did not think this was possible as even though Kangaroos have 2 teats they usually have the older joey drinking a different milk from one teat while the young one is attached to the other teat in the pouch.
If it is her first joeys, maybe 2 can attach as the second teat is not in use. Wonder what will happen when she has her next one when the two older ones are still drinking.
I plan to go to the zoo today, I will ask. I have seen photos on the net where a female kangaroo has 3/4 teats and the newly born joey latches on. I have a photo where a joey popped out and the pouch did,nt seal right away, I,ll put it on and you can decide if its another joey in there