[Alouette]

a true story about a pair of male penguins that became mates and raised a baby penguin

The male penguins did not "become mates." They bonded with the baby penguin and when it was old enough to go out on its own, they took female mates.

[Greg F]

The male penguins did not "become mates."

And if they did . . . well . . . yuck.

[Varda]

“The male penguins did not “become mates.”

Exactly. It sounds like this book means to confuse children on what a mate and therefore a family actually is.