Rao Gujarmal Singh became king of Rewari after his brother Rao BalKishan died in Battle Of Karnal. In his rule the kingdom was three times larger than that was in Rao Nandram's Rule , his state expanded to Karnal on one side , Bairath on other side in south, Mewat in the east and Hisar on west. Rao defeated Nawab of Farrukhnagar at Hansi and acquired estates of Hisar and area adjoining it. He was also Friend of Surajmal , Jat King of Bharatpur. Baloch Raja of Farrukhnagar and Bahadur Singh of Ghasera, a descendant of Hathi Singh, were both fierce enemies of Rao Gujarmal. Bahadur Singh was ruling independent from Raja Surajmal of Bharatpur. Then Rao Gujarmal along with Surajmal gave a befitting reply to him. Gujarmal also had friendly relations with Todar Mal of Neemrana, father-in-law of Bahadur Singh. In 1750, Todarmal invited Rao Gujarmal at the behest of Bahadur Singh and killed him by deceit.