And Tango makes three

And Tango makes three 
by Justin Richardson; Peter Parnell
illus. by Henry Cole 
Language: English 
New York : Simon & Schuster Books for Young Readers, ©2005. 
1 v. (unpaged) : col. ill. ; 23 x 29 cm.
ISBN: 0689878451; 9780689878459
$9.99
Readling level: Ages 4-8
Summary: At New York City's Central Park Zoo, two male penguins fall in love and start a family by taking turns sitting on an abandoned egg until it hatches.
Review: Central Park Zoo penguins Roy and Silo act like their male/female counterparts and do everything together. Watching the other penguin pairs build a nest, they too build a nest, but unlike the other penguins, their nest remains empty until one day their zookeeper finds an egg that needs to be cared for and brings it to their nest, where it eventually hatches, and Roy and Silo become parents together. Wonderful and clear illustrations. Included on this list because this story can be used as a metaphor for embryo donation and for same sex couples. 
Available: http://www.amazon.com/Tango-Makes-Three-Justin-Richardson/dp/0689878451/ref=sr_1_1?s=books&ie=UTF8&qid=1353843299&sr=1-1&keywords=and+tango+makes+three+by+justin+richardson+and+peter+parnell