As stated in the Brahma-saṁhitā (5.37):

When Kṛṣṇa descends anywhere, He is accompanied by His own associates. These associates are not ordinary living beings. Kṛṣṇa’s pastimes are eternal, and when He descends, He comes with His associates. Therefore Nanda and mother Yaśodā are the eternal father and mother of Kṛṣṇa. This means that whenever Kṛṣṇa descends, Nanda and Yaśodā, as well as Vasudeva and Devakī, also descend as the Lord’s father and mother. Their personalities are expansions of Kṛṣṇa’s personal body; they are not ordinary living beings. Mahārāja Parīkṣit knew this, but he was curious to know from Śukadeva Gosvāmī whether it is possible for an ordinary human being to come to this stage by sādhana-siddhi. There are two kinds of perfection—nitya-siddhi and sādhana-siddhi. A nitya-siddha is one who is eternally Kṛṣṇa’s associate, an expansion of Kṛṣṇa’s personal body, whereas a sādhana-siddha is an ordinary human being who, by executing pious activities and following regulative principles of devotional service, also comes to that stage. Thus the purpose of Mahārāja Parīkṣit’s inquiry was to determine whether an ordinary human being can attain the position of mother Yaśodā and Nanda Mahārāja. Śukadeva Gosvāmī answered this question as follows.