So in these two chapters, the sons of Shurasena are described. They are Vasudeva, Devabhāga, Devaśravā, Ānaka, Sṛñjaya, Śyāmaka, Kaṅka, Śamīka, Vatsaka and Vṛka. Apart from them, Vasudeva has five sisters: Pṛthā, Śrutadevā, Śrutakīrti, Śrutaśravā and Rājādhidevī. These 10 brothers and 5 sisters married (obviously) and had children.
Vasudeva, according to Srimad Bhagavatam married Devakī, Pauravī, Rohiṇī, Bhadrā, Madirā, Rocanā, Ilā and others (who include Devaki's sisters Śāntidevā, Upadevā, Śrīdevā, Devarakṣitā, Sahadevā, and Dhṛtadevā).
On the other hand, Harivamsa gives a list of 14 wives: Rohini, Indira, Vaishakhi, Bhadra, Sunamni, Sahadeva, Shantideva. Srideva, Devaki, Vrikadevi, Devarakshita, Upadevi, Sutanu and Badava.
Since these lists have a few common names, let us assume that each wife had two names.
Now both the sources list out Vasudeva's children. Since the Harivamsa account is a bit different, I quote only the Bhagavatam.
SB 9.24.46 — Vasudeva, by the womb of his wife Rohiṇī, begot sons such as Bala, Gada, Sāraṇa, Durmada, Vipula, Dhruva, Kṛta and others. SB 9.24.47-48 — From the womb of Pauravī came twelve sons, including Bhūta, Subhadra, Bhadrabāhu, Durmada and Bhadra. Nanda, Upananda, Kṛtaka, Śūra and others were born from the womb of Madirā. Bhadrā [Kauśalyā] gave birth to only one son, named Keśī. SB 9.24.49 — Vasudeva, by another of his wives, whose name was Rocanā, begot Hasta, Hemāṅgada and other sons. And by his wife named Ilā he begot sons headed by Uruvalka, all of whom were chief personalities in the dynasty of Yadu. SB 9.24.50 — From the womb of Dhṛtadevā, one of the wives of Ānakadundubhi [Vasudeva], came a son named Vipṛṣṭha. The sons of Śāntidevā, another wife of Vasudeva, were Praśama, Prasita and others. SB 9.24.51 — Vasudeva also had a wife named Upadevā, from whom came ten sons, headed by Rājanya, Kalpa and Varṣa. From Śrīdevā, another wife, came six sons, such as Vasu, Haṁsa and Suvaṁśa. SB 9.24.52 — By the semen of Vasudeva in the womb of Devarakṣitā, nine sons were born, headed by Gadā. Vasudeva, who was religion personified, also had a wife named Sahadevā, by whose womb he begot eight sons, headed by Śruta and Pravara. SB 9.24.53-55 — The eight sons born of Sahadevā such as Pravara and Śruta, were exact incarnations of the eight Vasus in the heavenly planets. Vasudeva also begot eight highly qualified sons through the womb of Devakī. These included Kīrtimān, Suṣeṇa, Bhadrasena, Ṛju, Sammardana, Bhadra and Saṅkarṣaṇa, the controller and serpent incarnation. The eighth son was the Supreme Personality of Godhead Himself — Kṛṣṇa. The highly fortunate Subhadrā, the one daughter, was your grandmother.
So, according to Srimad Bhagavatam, Vasudeva had all these children.
Yet, in something called Tenth Canto of a scripture called Srimad Bhagavatam, none of these wives or their children appear on the scene. In fact, even Rohini's son is Balarama, while the rest are absent. We can argue that they were born after Kamsa's end, but then wouldn't it be too much for Rohini and the others to be having children while Mathura is under war 17 times due to Jarasandha and his 23 Akshauhinis?
So, the basic question is: Wherefrom did these children spring forth, and into what did they return when Krsna was busy performing his leelas?