Kem was born in New York City (on St. Luke's Place), moved to New Hampshire when she was 14, and now lives in Washington, DC, with Jon (her husband) and a dog named Shadow. She loves spending time with her family—seven grandchildren, three daughters, and two sons-on-law. Other favorite things: long walks, movies, libraries, holidays, and cooking (for lots of people or just a few people. She likes to travel for research—and for fun.

Kem writes books for young people, as well as reviews and travel articles. (See the Dorling Kindersley (DK) Eyewitness Travel Guide to Washington if you're planning to visit the nation's capital! Highly recommended: "Three Guided Walks.") Her feature stories have appeared in Cobblestone, Scholastic News, The Five Owls, the St. Louis Post Dispatch, the Christian Science Monitor, and the Washington Post.

Kem's most recent books are Grace Akallo and the Pursuit of Justice for Child Soldiers, Champion of Freedom: Nelson Mandela and Champion of Freedom: Mohandas Gandhi. Her other biographies include Abigail Adams, Eleanor Roosevelt, Anne Frank, Lucretia Mott: Friend of Justice, and Marjory Stoneman Douglas: Guardian of the Everglades. She has also written The Underground Railroad in American History and Refugees: Seeking a Safe Haven, as well as a novel, Freedom Calls: Journey of a Slave Girl.

Kem has taught English and drama in K-12 in St. Louis Washington, D.C., as well as writing in the BFA program at the Corcoran College of Art + Design. She also worked at the Pulitzer Center, a journalism and education organization, where she was a contributing editor and mentored university students who received fellowships to report on global issues.