And Tango makes three

Tango : the true story of the very first chinstrap penguin to have two daddies 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
Awards: ASPCA Henry Bergh Children's Book Award, 2005; American Library Association Notable Children's Book, 2006; Gustavus Myer Outstanding Book Award, 2006 ; Nick Jr. Family Magazine Best Book of the Year, 2006; Bank Street Best Book of the Year, 2006.
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. 
Available: http://www.amazon.com/Tango-Makes-Three-Justin-Richardson/dp/0689878451/ref=sr_1_1?s=books&ie=UTF8&qid=1354716619&sr=1-1&keywords=9780689878459