Since we are somehow into Mohammed's fertility, I found this in Wikipedia,on the topic of "Genealogy of Khadija's daughters". I have copied & pasted this bit:
Muslim viewRegardless of which marriage they where born in, both Shi'a and Sunni view all the children with the high respect.
[edit] Sunni view
Sunni outright reject any notion of them being born anywhere but in Muhammad's marriage. Sunni honour Uthman as "possessor of the two lights", in reference to him being married to two of Muhammad's biological children.
Sunni believe that Ruqayyah was born three years after the birth of Zainab, when Muhammad was 33 [2]. Many Sunnis hold that the claim that Fatima is the only biological daughter is pushed by the Shia in order to strengthen the legitimacy of the Shia Imams. If there were other biological sisters who had children, then they would have as much a right to claim the caliphate then Fatima's descendants.
[edit] Shi'a view
Shia scholars view them as born in previous marriages[3], and that this fact is obscured in order to give greater merit to the first Banu Umayyad Caliph. Those Shi'as view is that Fatimah was Muhammad's only biological daughter and the only one who married a Caliph, i.e., Ali. They argue it improbable for Khadija to have given birth to so many children at such an advanced age, while at the same time having abstained from having children in both her previous marriages. A third version also exists which views the two daughters as being the children of Khadijah's deceased sister [4].
One source states:
? Who were Khadija's children by her second husband? This is another controversy that revolves round the other daughters or step-daughters of Muhammad besides Fatima. These daughters, chronologically arranged, are: Zainab, Ruqayya, and Ummu Kulthoom. Some historians say that these were Khadija's daughters by her second husband, whereas others insist they were her daughters by Muhammad. The first view is held by Sayyid Safdar Husayn in his book The Early History of Islam wherein he bases his conclusion on the contents of al-Sayyuti's famous work Tarikh al-khulafa wal muluk (history of the caliphs and kings). We hope some of our Muslim sisters who read this text will be tempted to research this subject. [5] ?
Ali Asgher Razwy, a 20th century Shi'a twelver Islamic scholar states:
? It is not known with any degree of certainty who were these three girls. Most of the Sunni historians claim that they were the daughters of Muhammad and Khadija. According to some other historians, they were the daughters of Khadija by an earlier marriage.
The Shia Muslims disagree. They assert that Zainab, Ruqayya and Umm Kulthoom were not the daughters of Muhammad and Khadija; in fact, they were not even the daughters of Khadija by any earlier marriage; they were the daughters of a (widowed) sister of Khadija. Khadija's sister also died, and upon her death, she brought the three girls into her own house and brought them up as her own children.
According to the Shia Muslims, Muhammad and Khadija had three and not six children.The first two of them ? Qasim and Tayyeb or Tahir ? were boys, and both of them died in their infancy. Their third and the last child was a girl ? Fatima Zahra. She was their only child who did not die in infancy.
The girls ? Zainab, Ruqayya and Umm Kulthoom ? could not have been the daughters of the Prophet of Islam. If they were, he would not have given them in marriage to the idolaters which the husbands of all three of them were. It's true that all three girls were married long before the dawn of Islam. But then he did not violate any of the imperatives of Qur?an at any time ? before or after he was ordained God's Messenger. And Qur?an is explicit on the prohibition of the marriage of a Muslim woman to a pagan. [6]
?
Shi'a argue that there is a lack of narrations from Muhammad regarding his other daughters, and they use it to argue that if they held the same position in Muhammads eye, this would not be the case:
Answering-Ansar states:
? If anything this serves as the greatest proof that Sayyida Fatima (as) was the sole daughter of Rasulullah (s). If these daughters indeed existed then Rasulullah (s) would have certainly apportioned them their share of inheritance as he had done with Sayyida Fatima (as). The very fact that we have no historical evidence of him ever giving them anything as a gift / inheritance is the clearest evidence that they did not exist. If they did exist then we have to accept that Allah (swt) and his Prophet (s) were unjust. After all the same Prophet (s) who marries Sayyida Fatima (as) according to revelation from Allah (swt) marries the other three daughters to kaafirs!
The same man that showered all manner of honour on Sayyida Fatima deeming her pain to be on par with his, giving her the title Leader of the Women of Paradise does not bother to relay even a single Hadith in praise of his other daughters. Ahl'ul Sunnah's authority work Mishkat al Masabeeh, under the Chapter 'Bab Fadail Ahl'ul bayt' has 49 traditions with regard of the relatives of Muhammad including his uncle Abbas, even his adopted son Zaid. Curiously the author of a book that takes traditions from TEN esteemed Sunni works fails to cite even a single Hadeeth on the "other daughters" in this chapter. ... The truth is that Maula 'Ali ( was the only son in law of Muhammad as we read in 'Riyadh al Nadira' Volume 3 page 220, Dhikr Fadail 'Ali:
Rasulullah said to 'Ali 'You possess three virtues not possessed by anyone else:
You have a father in law like me.
You have received my truthful daughter as your wife
You have received pious sons such as Hassan and Husayn
... This virtue (Rasulullah being father in law) would not be exclusive if Rasulullah also had other son in laws! If Nawasib try to argue that Uthman's marriage may have occurred later we should point out that according to the Ahl'ul Sunnah the daughters of Rasulullah were married long before Sayyida Fatima, and were the wives of two of Abu Jahl's sons. Rasulullah could not have praised 'Ali for this exclusive honour if he had other sons in law. ... The famed title of Uthman 'Dhul Nurayn' coming from the mouth of Muhammad(as asserted by sunnis) is not present in any of the six esteemed works of Ahl'ul Sunnah. When the very existence of these daughters cannot be established then how can we accept that Uthman was the possessor of two lights? ... It is indeed ironic that the Salafi and Deobandi Nawasib reject the notion of Muhammad being created from Nur (Light), rather they deem him an ordinary human like us created from mud. Curiously when it comes to honouring Uthman suddenly he is deemed Dhul Nurayn 'the possessor of two lights'. If Prophet (s) is not 'Light' then how can Uthman become the possessor of 'Two Lights'? How can this then be used as an excuse that he married the 'supposed' two daughters of Muhammad? [7]
Rashna wonders If Ruqayyah was born when Mo was 33, Khadija would be 48. Isn't this a very advanced age to have kids back in the days when there were no fertility treatments & donor eggs? If we are into Mo's fertility, a rather unneccessary topic, we might just as well discuss Khadija's fertility too!
Topic: Do you know all the answers?