Walter Breuning was born in Melrose, Minnesota to John Breuning and Cora Morehouse Breuning on 21 September 1896, and had four siblings, two sisters, and two brothers. Later on in life, he claimed to have memories from the 1800s, with his earliest memory he could recall being of his grandfather, a Civil War veteran, telling him stories from the war.
In 1901, when he was only 4 or 5, his family moved to De Smet, South Dakota, where he went to school for 9 years until his family broke up in 1910 when Breuning was 14. His family lived without electricity, water, or plumbing. Although his parents died at only 50 and 46, longevity was still present in Breuning’s family. His paternal and maternal grandparents all lived into their 90s, and his siblings lived to the ages of 78, 85, 91, and 100.