I work on fossil mammals, so I am thrilled to answer your question. There are three big branches on the mammalian evolutionary tree. One includes the egg-layers (called monotremes, and which include the platypus and spiny anteaters--also known as echidnas). A second branch, the placental mammals, which includes all the mammals that live around here (except one), including whales, bats, porcupines, gophers, coyotes, and MANY more. And last, the marsupials, which is what kangaroos and opossums are. Placentals and marsupials both give birth to live young, rather than laying eggs, but the newborns of marsupials are generally much more "premature" (or helpless--altricial is the real word) than are those of placentals. For example, baby horses generally stand within one hour of being born.

So indeed, kangaroos and opossums are closely related, since they're both marsupials. Why do they live so far apart you might ask?

Well....paleontologists believe that marsupials originated in Asia (where they don't live today). From there they made it to North America, where they hung out with such famous neighbors as Tyrannosaurus and Triceratops. From North America (where marsupials also eventually became extinct), they made it to South America, where they diversified into various different kinds, most, unfortunately also now extinct. From, there, roughly 60 million years ago, they reached Australia via Antarctica--those landmasses were much closer then than they are now. Those early marsupials in Australia evolved into a kaleidoscope of forms, like kangaroos, koalas, possums (different than opossums, which live in the Americas) and Tasmanian wolves), after Australia ripped away from Antarctica, leaving its mammals isolated.

The last piece of the puzzle is explaining where the opossum that lives around here, and indeed over much of North America, came from. It's the one non-placental mammal in these parts here today. Believe it or not, it's a fairly recent immigrant from South America. Central America emerge above sea level about three million years ago, allowing animals like the opossum, porcupines, and giant ground sloths (now extinct) to spread north, and things like elephants (in the form of mammoths), saber-tooth cats, and horses to move south.

So, now you know the story of the kangaroo and opossum--very distant marsupial cousins.

Stay curious and keep asking great questions! Be well,

You are thinking like a biologist. We often want to know which species are most closely related. All species on Earth are related, but some are more closely related than others.

Mammals include all animals that have fur and give milk. This includes marine mammals such as whales, which only have fur before they are born. There are 3 main groups of mammals. One group lays eggs. It includes the duck-billed platypus and the spiny anteater (echidna). When these babies hatch, their mother feeds them with milk. They are called monotremes.

The other group includes all the mammals that have live birth. That group is divided in to marsupials, which carry babies in pouches, and placental mammals, which don’t. The North American opossum is the only marsupial in the USA. It is more closely related to kangaroos and koalas than it is to raccoons or rats. You can learn more about marsupials at this site:
marsupials.

What do you think are some advantages and disadvantages to having babies born extremely young, compared with them staying inside the mother much longer?

Kangaroos and american oppossums both belong to the mammalian group Marsupialia (marsupials).

Marsupials all share the characteristic of birthing their young early; rather than developing over a longer period in the uterus (as in humans); marsupials crawl from the womb to an external pouch where they have access to mammary glands and continued protection from the mother.

The ancestors of American opossums and all Australian marsupials were separated, allowing these two groups to evolve independently. Within Australian marsupials there is a group called Diprotodontia, which contains kangaroos, koalas, and Australian possums, which look similar to American opossums.

So yes! Kangaroos and opossums are related; but kangaroos share much more in common with Australian possums and koalas.

Opossums and kangaroos are both marsupials. The marsupial is a group of mammals that do not have a placenta, the organ that allows gas and nutrient exchange between the developing fetus and the mother, and carry their young in a pouch. In this sense, opossums and kangaroos are more closely related than all other placental mammals.

However, marsupial is also a big group with 334 living species. For reference, there are about 190-448 species of living primates. The difference between an opossum and a kangaroo is comparable to the difference between a human and a lemur.

Opossums and kangaroos are both marsupial mammals, but are quite distantly related within the marsupial mammal group. As such, they are more closely related to each-other than either is to human beings, but among marsupials, they aren't very close. Kangaroos in particular are much closer related to other Australian marsupials, such as Tasmanian devils and many others.

Under the current biological classification system, kangaroos and opossums are both marsupials. The classification of marsupials, Marsupialia, is what we call an infraclass. The differences among infraclasses are in the reproductive system. When we look at the biological classification system from broadest to narrowest - Kingdom, Phylum, Class (the infraclass), Order (then suborder), Family, Genus, Species - we see that kangaroos and opossums are related on the level of infraclass, but not on lower levels.

Yes.

Kangaroos and opossums are members of the same animal family. Both animals are marsupials, so they have pouches. Marsupial mothers carry their babies in these pouches.