I didn't understand the article but this part is interesting:

The side-vadges are where sperm — from the males’ two-pronged penises — travel up, the middle-vadge is where the baby joey slides down to develop externally in the mother’s pouch after growing to the size of a jellybean in one of her two uteri. Fun fact: Female kangaroos can be “perpetually pregnant” because of how their plumbing works. Because once one joey has left a uterus for the pouch, another embryo can go ahead and start developing internally. So, basically, kangaroos can be pregnant forever.

Source: https://www.themarysue.com/kangaroos-have-three-vaginas/