It's possibly the most adorable banned book some children will never see. It's a story about love, family, and a fuzzy baby penguin whose parents have waited for her for years. Yet, And Tango Makes Three, the true story about a family of penguins at New York’s Central Park Zoo, has been among the top ten challenged books in the United States seven times (and was the most challenged book of the year for four of those times).

Were Tango's parents just a little bit different, perhaps the story would be praised as a beautiful tale of parents overcoming odds to bring a child into the world. Tango’s parents, you see, wait for a baby for a long time. A year after they meet, Tango’s parents build a nest, bring over a rock, and wait desperately for a baby penguin to hatch. They take diligent care of the rock, trading off who sits with it and keeps it warm, and never seeming to give up hope that one day they’ll have the baby for which they dream. When another pair of penguins have two eggs – one of which they won’t be able to hatch on their own – Tango’s parents adopt the egg and, after 34 more days of tender, unyielding care, Tango is born. The trio huddle together, finally a family.

But Tango’s parents are named Roy and Silo, and they’re both males. And so, almost immediately after it’s released, the sweet picture book detailing their story went straight to the top of the ALA’s list of most frequently challenged books. Year after year, this story of a family – which, it should be noted, only briefly mentions that Roy and Silo are both males – is labeled as “anti-family,” “promoting the homosexual agenda,” and “unsuitable for the age group.”

To reiterate: A children’s picture book. About real-life penguins. Trying desperately to create a family. Is “anti-family” and “unsuitable for the age group.” At the same time, parents lamenting the increasing acceptance of LGBT adults and children wonder how they’ll ever be able to explain same-sex marriage and “alternative families” (whatever that might mean) to their children. Explaining same-sex marriage to children might be a difficult task, indeed, if a story of a loving penguin family is seen as too inappropriate an inroad.

And Tango Makes Three highlights why we must never believe that the era of banning books is over. When Heather Has Two Mommies was released in 1989, it faced many of the same complaints lobbed at And Tango Makes Three year after year. It became the 11th most challenged book of the 1990s (a controversy parodied in the Captain Underpants series, which itself shows up repeatedly on the list of most frequently banned books).  And, for many of us, it started a national conversation about families that has reverberating effects even today. Today’s schools are filled with children who, like Tango, are the long-held dream of parents who want to raise children of their own. Yet, some parents– many of whom were in elementary school when Heather Has Two Mommies was being struck from their shelves – believe that this story about a penguin family is a step too far. And Tango Makes Three may make some adults uncomfortable. But it also provides comfort to the many children who want to see their own families mirrored, and that’s exactly why it needs to remain on library shelves.

And anyway, how can you not love a story about penguins?