His birthday was on Aug. 9th.

He lives in Brooklyn. His wife is artist Elaine Longtemps.
He's illustrated books by Florence Parry Heide, Ann McGovern, Nina Bawden, Barbara Shook Hazen, and Dahlov Ipcar.
https://www.google.com/search?sca_esv=557881931&q=%22kenneth+longtemps%22&tbm=isch&source=lnms&sa=X&ved=2ahUKEwj1zNiA0uSAAxVVkIkEHfGBBTAQ0pQJegQIBRAB&biw=1293&bih=813&dpr=1
(book covers)

Josie, Con Amore by Milla Logan, 1966
("...novel about a San Francisco restaurant owner who can't resist helping people-even when they don't know they're in trouble.")

The White Horse Gang by Nina Bawden, 1966
("Story for older children about the adventures of a gang, a haunted wood and white mare.")

A Rainbow For Robin by Marguerite Vance, 1966
http://covers.openlibrary.org/w/id/6706503-M.jpg
(cover)
("...story of a young blind girl who learns to read music in braille and becomes an expert pianist. Based on the life of a real girl.")

General Felice by Dahlov Ipcar, 1967
("Two girls on a summer farm in Connecticut, their horses, and their enemies." )

GREEK MYTHS AND LEGENDS: LITERARY HERITAGE SERIES, retold by James R. Squire and Barbara L. Squire, 1967
https://www.amazon.com/GREEK-MYTHS-LEGENDS-EMINENT-MYTHOLOGISTS/dp/B000O8SG5E
(book cover)

The Chalet at Saint-Marc by Suzanne Butler, 1968
("Tale of the courage & self-reliance of 4 young people fighting a bitter Alpine storm on their own.")

The Day it Snowed in Summer by FlorenceParry Heide & Sylvia Van Clief, 1968
("Everybody in New York City, including Carrie & Loretta Cecelia (her doll), was complaining about the terrible hot day when somebody made a mistake & it snowed."...."Carrie & her doll are friends of Jack Frost.")

Our Tree by Herbert H. Wong & Matthew F. Vessel, 1969
("....the reader soon finds out what else a tree is for: it's for exploring, investigating, and learning. The family to whom the tree belongs discovers a world of animal life in and around it, and watches the seasonal cycle of the tree itself.")

Danny Dougal the Wanting Boy by Barbara Shook Hazen, 1970
(http://s.ecrater.com/stores/23477/46587d1f33df6_23477b.jpg)
("Danny always wants everything he sees until his rich uncle proceeds to give it to him.")

Sound of Sunshine, Sound of Rain by Florence Parry Heide, 1970
http://www.yesterdaysgallery.com/pictures/15237.jpg
(big cover)
("An uncommon title by Florence Parry Heide; made into an animated short film which was nominated for an Oscar in 1984.")

Our Terrariums (Science series for the young) by Herbert Wong, Matthew F. Vessel, 1971

Sometimes I Dance Mountains by Byrd Baylor, 1973
http://ecx.images-amazon.com/images/I/51PrAr2gLsL._SL500_SY300_.jpg
(cover)
("It includes photos of a child in a dance class in Tucson, AZ, making modern dance movements according to how she feels and how her surroundings are affecting her.")

The Stairs That Kept Going Down by Sir Compton Mackenzie, 1973
http://images.alibris.com/imageid/2000784441_t.jpg
(cover)
("In the London house his family occupies, a ten-year-old boy discovers a secret, seemingly endless, staircase that leads him to the scene of a crime.")

The Secret People by Madelaine Duke, 1974
("Four young men face the conflicts of Australia's immense Red Center on camelback and discover the compromises they must make in a less civilized climate.")

The Magic Pot: An African Folktale retold by Ann McGovern, 1975
http://ecx.images-amazon.com/images/I/510esBeZXML._SL500_SX300_.jpg
(cover)
("With the help from a magic pot, a boy becomes the best trader in all of Africa.")

Exploring Music by Beth Landis, Barbara Andress, Eunice Boardman, 1975
http://ecx.images-amazon.com/images/I/41S7EZ4FWVL._AA115_.jpg
(cover)

The Finding by Nina Bawden, 1985
("An adopted English boy inherits a lot of money from a lady who was probably his real grandmother, causing him to run away.")