During the creation of universe, from his mental powers Brahma created ten sons. Their names were Bhrigu, Pulastya, Pulaha, Kratu, Angira, Marichi, Daksha, Atri, Vashishtha and Rudra. The first nine became sages and were known as the original brahmanas.
To ensure that creation progressed. Brahma divided his own body into two halves. The male half was known as Svayambhuva Manu and the female half was known as Shatarupa. These two married and had two sons named Priyavarata and Uttanapada. They also had two daughters named Akuti and Prasuti.
Prasuti married Daksha and they had twenty-four daughters. These twenty-four daughters became the mothers of all living beings. Thirteen of the daughters were married to Dharma. Of the remaining eleven daughters, Sati was married to Shiva (Rudra); Khyati to Bhrigu; Sambhuti to Marichi; Smriti to Angira; Priti to Pulastya; Kshama to Pulaha; Sannati to Kratu; Anasuya to Atri; Urjja to Vashishtha; Svaha to Agni; and Svadha to Agni; Svadha to the ancestors (pitris).
Brahma told Shiva, “Why don’t you create some beings?”
Shiva agreed with alacrity. But all the beings whom Shiva created were just like him in form. That is, they were immortal.
“What are you doing?” exlaimed Brahma. “Don’t create beings who are immortal. Create those that are mortal.”
“I will not create mortal beings,” replied Shiva.
“Then stop creating.” responded Brahma. “I will take care of creation myself.”
Shiva ceased to create. But the beings whom he had already created came to be known as the rudras. They were given rights to offering made at sacrifices, together with the other gods.