kṣatra-bandhuś ca nāhuṣaḥ
According to the Vedic system, marriages between kṣatriyas and kṣatriyas or between brāhmaṇas and brāhmaṇas are the general custom. If marriages sometimes take place between different classes, these marriages are of two types, namely anuloma and pratiloma. Anuloma, marriage between a brāhmaṇa and the daughter of a kṣatriya, is permissible, but pratiloma, marriage between a kṣatriya and the daughter of a brāhmaṇa, is not generally allowed. Therefore Mahārāja Parīkṣit was curious about how Śukrācārya, a powerful brāhmaṇa, could accept the principle of pratiloma. Mahārāja Parīkṣit was eager to know the cause for this uncommon marriage.