Stevens was born on February 2, 1868, in North Andover, Massachusetts, to Horace Nathaniel Stevens (1837–1876) and Susan Elizabeth (née Peters) Stevens (1835–1871). He was the seventh generation descendant of John Stevens, who came to the United States in 1638.[1] His paternal grandfather was Nathaniel Stevens (1786–1865). His uncles were U.S. RepresentativeCharles Abbot Stevens (1816–1892), Moses Tyler Stevens (1825–1907), and George Stevens (1832–1871).
On February 12, 1895, married Edna Ten Broeck (1874–1964), the daughter of Rensselaer Ten Broeck (1838–1918) and Phebe (née Wilson) Ten Broeck (1846–1916). Together, they had three sons:[1][4]
John Peter Stevens, Jr. (1897–1976), who married Edith Stevens (1899–1989). President of the Edison Township Board of Education from 1943 to 1958, President of John P. Stevens and Co. and namesake of J.P. Stevens High School in Edison, New Jersey[5]