The sister group of Eutheria is Metatheria.

Eutheria, Metatheria, and Prototheria

Eutheria / placental mammals

Metatheria / marsupials

Prototheria / monotremes

Prototheria is the subclass containing the egg-laying mammals (the echidna and platypus). Metatheria is the subclass that encompasses marsupials and a few other now-extinct mammals that were not placental. The other subclass of mammals is Eutheria, which contains all placental mammals, which make up the majority of mammals.

Yes, they have very well developed pouches, also called a marsupium. Microbiotheria or Monito del monte are in the subclass Metatheria who are known to usually have pouches.