 Bhai Sati Das was his younger brother.Bhai Mati Das was the son of Hira Nand, a disciple of Guru Har Gobind, under whom he had fought in many battles and was a great warrior.Hira Nand was the grandson of Lakhi Das, the son of the Bhai Praga, who was also a martyr and had been a "Jathedar" (leader) in Guru Hargobind's first battle.