Are cats marsupials

No: cats are placental mammals. Marsupials are those mammals that rear their young in pouches, for example a kangaroo.

Specifically, marsupials are characterised by bearing very undeveloped young. Not all marsupials raise their young in a pouch. the numbat of Western Australia, for example, does not have a pouch, but the undeveloped young latch onto a teat on the mother's underside, and cling to her belly with sharp claws for several months.