Ten sons were born of the womb of Dyou, sired by Brahmā (Brahma). Ṛchīka (Richika) was one of them. In one sense, Brahmā is also called Vivasvān (Vivaswan). Nīlakaṇṭha (Nilakantha), the commentator has said that the sons of Dyou, as depicted in masculine gender, denotes Vivasvān Sūrya (Vivaswan Surya; the Sun-god), that is, they are the sons of Vivasvān who is referred to here as Brahmā —
pureti purākalpe ete divaḥ putrādayaḥ
puṁśabdā vivasvato vāchakā paṭhyante purākalpavidbhiḥ.