What is the biological family that contains every living penguin species?

The biological family containing every living penguin species is Spheniscidae.

Spheniscidae is the family name used in zoological classification for living penguins. All modern penguins are flightless seabirds within this family, although they retain wings that have evolved into rigid flippers for underwater propulsion.

The family is placed in the order Sphenisciformes. Those two names are easy to confuse: Spheniscidae is the family, while Sphenisciformes is the order. The family includes genera such as Aptenodytes, Pygoscelis, Eudyptes, Eudyptula, and Spheniscus.

Fossil penguins show that the group was once more diverse than it is today. Modern species range from the tiny little penguin to the much larger emperor penguin, but all share adaptations for marine life and insulation.