All marsupials have a 'doubled' reproductive tract: two vaginas, two uteri, two cervixes, two oviducts, but with only one external vaginal opening.
The two vaginas are for sperm delivery. For birth, female marsupials have a spontaneous third vagina!
Image from https://www.nationalgeographic.com/science/article/kangaroos-have-three-vaginas#:~:text=Koalas%2C%20wombats%20and%20Tasmanian%20devils,down%20to%20the%20outside%20world.
In some species, this vagina is permanent after the first time a female gives birth, such as in kangaroos and wallabies.
In almost all other marsupial species, this third vagina is temporary; it forms just before birth and disappears shortly after. It will reform with each pregnancy.
Reproductive tracts of estrous (A) and anestrous (B) female opossums.
Image from Harder & Jackson 2003
The males have a correspondingly double penis that ejaculates sperm into the two vaginas.
Image from https://echidnawalkabout.wordpress.com/2017/04/26/5-facts-about-koala-sex/
References and Further Reading