Kenneth Hazen Aynesworth, surgeon and regent of the University of Texas, son of George Levin and Ellen (Hickman) Aynesworth, was born at Florence, Texas, on February 9, 1873. He attended Baylor University (1892–94) and graduated from the University of Texas Medical Department in 1899. As a medical student, Aynesworth was a member of Alpha Mu Pi Omega medical fraternity and Alpha Omega Alpha honorary medical fraternity. He interned in 1899–1900 and served as house surgeon, 1900–01, at John Sealy Hospital, Galveston. In 1901 he also served as demonstrator in anatomy at the University of Texas Medical Department. Aynesworth took postgraduate courses at Friedrich Wilhelm University in Berlin (1902) and at Johns Hopkins University in Baltimore, Maryland (1909). In 1903 he began medical practice in Waco. He became consulting surgeon for the Missouri, Kansas and Texas Railroad (1906) and the Texas Electric Railroad (1910). He served on several city boards and commissions, including the Waco school board (1907–17) and board of health (1903–13). Aynesworth was a member of the McLennan County Medical Society (president, 1939), Texas State Medical Association, American Medical Association, American Board of Surgery, West Texas Archaeological and Paleontological Society, Texas Academy of Science, Texas State Historical Association, and a founder of the Philosophical Society of Texas. He was a charter member of the Texas Surgical Society (president, 1927) and was elected a fellow of both the Southern Surgical Association and the American College of Surgeons. He was a Baptist and Mason.
In 1933 Aynesworth received an honorary LL.D. from Baylor University and was appointed to the board of regents of the University of Texas. As a regent from 1933 to 1944 he served on the complaints and grievances committee, the medical branch committee, the library committee, the College of Mines (now the University of Texas at El Paso) committee, and the board of lease of university lands. He was instrumental in the acquisition of important new collections for the University of Texas Library on the subjects of Latin America and Texas History. As an avocation he collected Texana and American Indian artifacts. He donated both collections to Baylor University. On December 31, 1902, Aynesworth married Maud Bryan of St. Maurice, Louisiana; they had four children. He died on October 30, 1944, in Waco of a cerebral hemorrhage and was buried in Oakwood Cemetery, Waco.