Roy and Silo, two male penguins living in the Central Park Zoo, created a stir over a decade ago after they successfully hatched and adopted a chick named Tango. The little family then inspired the children’s book “And Tango Makes Three.”

That 2005 children’s story is back in the news this week after Singapore’s National Library Board announced it would be banning the book from its collection and destroying all existing copies.

“NLB’s collection development policy takes special care of our children’s collections to ensure they are age-appropriate. We take a cautious approach, particularly in books and materials for children,” the board said in a statement. “NLB’s understanding of family is consistent with that of the Ministry of Social and Family Development and the Ministry of Education.”

Notably, the other two children’s books banned by Singapore -- “The White Swan Express: A Story About Adoption” and “Who’s In My Family: All About Our Families -- also feature gay and lesbian characters.

Singapore's penal code includes a section criminalizing homosexual acts, though it is rarely enforced.

Many Singaporeans took to Twitter to protest the decision to bar the books from the collection, using the hashtag #FreeMyLibrary. Thousands of users have also signed an open letter to the government urging a repeal of the ban.

“Parents who object to the content of these books have the option of not borrowing them for their children,” a portion of the letter reads. “To withdraw it from circulation is irresponsible and unfair to other library users and parents who may want to teach their children about acceptance, tolerance, and the heterogeneity of family structures.”

Here in the United States, “And Tango Makes Three” has also repeatedly attracted controversy. The American Library Association notes that its often listed on its top ten list of frequently challenged books.

Roy and Silo aren't the only same-sex, male penguin couple believed to exist. Pedro and Buddy, seen here at the Toronto Zoo, are African penguins who exhibited mating behavior with each other. Zoo officials forcibly separated the two to pair them with females as part of a species survival plan for the endangered breed.MARK BLINCH / Reuters, file