Kottarathil Sankunni was born on March 23, 1855, at Kodimatha, in Kottayam district of the south Indian state of Kerala (erstwhile Travancore) to Vasudevan Unni-Nangayya couple. The boy, whose name at birth was Vasudevan but was called Thanku, Sanku and later Sankunni, did his early schooling under the tutelage of a local teacher and later, studied Sanskrit under Manarkattu Sanku Warrier and traditional medicine under Vayskara Aryan Narayanan Mooss. He joined Malayala Manorama in 1890 as the editor of their poetry section during which time he tutored a few Britishers the language of Malayalam. In 1893, he was selected as a Malayalam teacher at M. C. High School.
Sankunni married for the first time in 1881 but after the death of his first wife, married Evoor Panaveliveettil Sreedevi Amma in 1887. he married twice more, the brides were Panaveli Lakshmy Amma and Pengali Thekkethu Devaki Amma. He died on 22 July 1937, at the age of 82.