László was born on June 9th, 1850. László's father was János Körtvélyessy and his mother was Anna Kerékgyártó. His paternal grandparents were Mihály Körtvélyessy and Katalin Juhász. He had two brothers named János and László. He was the youngest of the three children. He had a half-sister named Teréz. He died at 11 months old on May 27th, 1851.