Diti‘s sons were known as the daityas (demons). Diti originally had two sons named Hiranyakashipu and Hiranyaksha. Hiranyakashipu was the elder.
Kashyapa once organized an ashvamedha yajna (horse sacrifice). All the gods and the sages came to attend this sacrifice. A golden throne had been prepared for the chief priest. Diti was also present on the occasion then. She had, at the time, been bearing a baby for ten thousand years in her womb. When all arrangements had been made for the sacrifice, the baby was born. The newly born baby ascended the throne reserved for the chief priest and immediately began to recite the Vedas. It was this baby who came to be known as Hiranyakashipu.
Hiranyakashipu hung upside down for one lakh years and prayed to Brahma. Through this period, he fasted. This act of tapasya so pleased Brahma that he granted Hiranyakashipu a boon whereby the demon became invincible. Thus fortified, Hiranyakashipu started to oppress the world. He drove the gods out of heaven. Hiranyakashipu was eventually killed by Vishnu in his narasimha (half-man half-lion) incarnation.
Hiranyakashipu had four sons named Prabhlada, Anuhlada, Samhlada and Hlada. Hlada‘s son was Sunda and Sunda‘s wife was Tadaka. It was this Tadaka whom Rama (in the Ramayana) killed. Tadaka‘s son was Muka. Muka was killed by Arjuna (in the Mahabharata). Prahlada‘s son was Virochana and Virochana‘s son was Vali. Vali was defeated by Vishnu in his vamana (dwarf) incarnation. Vali had a son named Vana.
As for Hiranyakashipu‘s brother Hiranyaksha, he had five sons. They were named Utkara, Shakuni, Kalanabha, Mahanabha and Bhutasantapan. Hiranyaksha was killed by Vishnu in his varaha (boar) incarnation.
Hiranyakashipu and Hiranyaksha had a sister named Simhika.
Diti noticed that her sons and their descendants were suffering at the hands of the gods, often with the connivance of Vishnu. She therefore did her best to please her husband Kashyapa. Kashyapa was eventually satisfied and agreed to grant Diti a boon.
―Please grant me the boon that I may have a son who will kill Indra.‖ said Diti.
This was slightly awkward for Kashyapa. The gods were also his sons, from his other wife Aditi. He told Diti that she would have to observe cleanliness for a hundred years. If she succeeded in doing this, she would indeed give birth to a son who would slay Indra. But if she failed, the son would become Indra‘s friend and companion. This condition Diti accepted.
Diti started to perform tapasya so that she might have the son she wanted. But Indra had got to know about what Diti was after. He hung around the hermitage, helping his aunt by fetching fruits, roots and wood from the forest. But this attempt at aiding his aunt was merely a pretext. Indra was the lookout for some unclean act that Diti might commit.
Ninety-nine of the hundred appointed years passed.
It was then that Diti made her first mistake. She was so tired that she fell asleep, resting her head on her thighs. In the process, her hair touched her feet. This was an unclean act. In a flash, Indra seized his opportunity. Now that Diti had committed an unclean act, he could freely enter her body. He entered Diti‘s womb and found the baby there. Indra possessed a weapon known as the vajra. With the vajra, Indra sliced up the baby into seven parts.
The parts began to cry and Indra said, ―ma ruda,‖ which means, ―don‘t cry.‖
But the parts continued to cry and Indra carved up each of the parts into seven more sections. There were thus forty-nine parts in all.
Meanwhile, Diti had woken up and she begged Indra not to kill her sons. Indra agreed. The sons were born. Because of the words indra had uttered, they came to be known as the maruts. Thanks to Kashyapa‘s boon, they became friends and constant companions of Indra. They were elevated to the status of gods.