According to Shaykh al-Mufid (Kitab al-Irshad):
The Commander of the Faithful, peace be on him, had twenty-seven children, male and female:
3. Zaynab the elder
4. Zaynab the younger, who was given the kunya Umm Kulthūm.
Their mother was Fāṭima, the blessed, mistress of the women of the worlds, daughter of the master of those sent by Allāh and the seal of the prophets, the Prophet Muhammad.
5. Muḥammad, who was given the kunya Abū al-Qāsim. His mother was Khawla, daughter of Ja‘far b. Qays al-Ḥanafī.
7. Ruqayya They were twins.
Their mother was Umm Ḥabīb, daughter of Rabī‘a.
11. ‘Abd Allāh
(The last four) were martyrs with their brother al-Ḥusayn on the plain of Karbalā’. Their mother was Umm al-Banīn, daughter of Ḥizām b. Khālid b. Dārim.
12. Muḥammad, the younger, who was given the kunya Abū Bakr.
13. ‘Ubayd Allāh
Both of these were martyrs with their brother al-Ḥusayn on that plain. Their mother was Layla, daughter of Mas‘ūd al-Dārimī.
His mother was Asmā ̓, daughter of ‘Umays al-Khath‘amī, may Allāh be pleased with her.
15. Umm al-Ḥasan
The mother of these two was Umm Sa‘īd, daughter of ‘Urwa b. Mas‘ūd al-Thaqafī.
18. Zaynab, the youngest
19. Ruqayya, the younger
20. Umm Hānī ̓
21. Umm al-Kirām
22. Jumāna, who was given the kunya Umm Ja‘far.
24. Umm Salama
These, the blessings of Allāh be on them, had different mothers. Among the Shī'a, there are those who mention that Fāṭima, the blessing of Allāh be on her, after the Prophet had a miscarriage with a son, whom the Prophet, may Allāh bless Him and His Family, had (already) named during her pregnancy as Muḥsin.
According to this group there were twenty-eight children of the Commander of the Faithful, the blessing and peace of Allāh be on him. Allāh knows and judges best.
(End quotation from Kitab al-Irshad)