The Barnwal family was started by King Ahivarn whose ancestors had moved to a place called Ahar in North India. Ahivarn renamed the Ahar kingdom after himself and founded its capital as "Varn-sahar" (in present day Bulandshahar Western UP). His children named as Varnwal, a term that distorted to Barnwal over the years. Barnwals were the oldest and most prominent families of the Bulandshahar region; directly descended from Raja Ahivarn.

 King Ahivarn/Ahibarn has been speculated to be a king of the Tomar caste. Although his dynasty was succeeded by Dors after hundreds of years, his family adopted his name, continued his lineage and were called Barnwals.

King Ahivarn was a Suryavanshi Kshatriya who was the 21st descendant of Emperor Mandhata, the ruler of Ayodhya. According to the methodological Mahalakshmi Vrat Katha, Ahivarn, the son of Prmaal, and the King Agrasen (son of King Vallabh) belong to the same lineage.

The supposed distruction of Varn-sahar or Barn-sahar during an attack by Muhammad Gauri in 1192 CE made the Barnwals avoid the city.

A large part community dispersed to different parts of Indiain later centuries. Some of Barnwals who were Zamindars and had received the title of Rai-Bahadur during the British rule in India, continue using Singh sirname. Many Barnwals have adopted generic sirnames such as Lal, Gupta, Prasad, Anand, Prakash & ubiquitous Kumar in order to socialize and intermingle with the society.

They were very orthodox Hindus. Wearing the sacred thread was common although in modern times this practice has declined.

Notable Barnwals in recent

---Mr. Shithikanth Barnawal, IIT-JEE 2008 Topper

---Mr. Vikas Barnwal, IIT-JEE 2001 Rank 38, CAT 2005 99.99 Percentile Rank 6