János' father was János Kósa and his mother was Zsuzsanna László. His paternal grandparents were János Kósa and <Unknown>. He had three brothers and a sister, named Péter, István, Mihály and Erzsébet. He was the second oldest of the five children. He died at the age of 59 on July 26th, 1854 in Aba Fejér vm.2