Srimad Bhagavatam Canto 09, Chapter 22, Text 25

SB 9.22.25

ksetre ’prajasya vai bhratur
 matrokto badarayanah
dhrtarastram ca pandum ca
 viduram capy ajijanat
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Badarayana, Sri Vyasadeva, following the order of his mother, Satyavati, begot three sons, two by the womb of Ambika and Ambalika, the two wives of his brother Vicitravirya, and the third by Vicitravirya’s maidservant. These sons were Dhrtarastra, Pandu and Vidura.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Vicitravirya died of tuberculosis, and his wives, Ambika and Ambalika, had no issue. Therefore, after Vicitravirya’s death, his mother, Satyavati, who was also the mother of Vyasadeva, asked Vyasadeva to beget children through the wives of Vicitravirya. In those days, the brother of the husband could beget children through the womb of his sister-in-law. This was known as devarena sutotpatti. If the husband was somehow unable to beget children, his brother could do so through the womb of his sister-in-law. This devarena sutotpatti and the sacrifices of asvamedha and gomedha are forbidden in the Age of Kali.
 
asvamedham gavalambham
 sannyasam pala-paitrkam
devarena sutotpattim
 kalau pañca vivarjayet
 
“In this Age of Kali, five acts are forbidden: the offering of a horse in sacrifice, the offering of a cow in sacrifice, the acceptance of the order of sannyasa, the offering of oblations of flesh to the forefathers, and a man’s begetting children in his brother’s wife.” (Brahma-vaivarta Purana).
Srimad Bhagavatam Canto 09, Chapter 22, Text 21-24
Srimad Bhagavatam Canto 09, Chapter 22, Text 26