For all the sex in the Quran and in Muhammad?s life, he had little to show for it. Only one surviving child, and no sons to carry on his legacy. The Sunni vs. Shiite rift is a direct consequence of Mohammad having no heir-apparent.
By comparison, let?s look at another well-known Arab family ? the bin Ladens. The patriarch of the family was Sheikh Mohammed bin Laden (died 1967). He had 22 wives and 55 children. From that start, there are now 600 descendants and their spouses. Osama bin Laden was his 17th child, and he went on to have five wives and twelve to twenty-four children. So, just between Osama and his father alone, they produced almost 80 children. The Prophet Muhammad had only one surviving child who died just six months after him.
This leads to another twist to the story of Muhammad?s sexual prowess, and it also implies that Muhammad was impotent. Muhammad?s nine surviving wives were quite young. Aiyisha, who he defrocked when she was nine and he was 54, was only eighteen when Muhammad died. The only wife who was not in her teens or twenties, was Sauda who was in her thirties when Muhammad died. Obviously, all of these women were still attractive and were still of child-bearing age. So was it an act of cruelty or an attempt to cover up his impotency when Muhammad?s wives forbidden to remarry after his death?
The Quran was quite explicit: ?The Prophet has a greater claim on the faithful than they have on each other. His wives are their mothers.? (Surah 33:6) Simply put, marrying a widow of Muhammad would be incest. This is reinforced in verse 53, which says, ?You must not speak ill of God?s apostle, nor shall you ever wed his wives after him; this would be a grave offence in the sight of God.? A more logical motive for this decree is that if the surviving widows began to have babies with their new husbands, it would be proof positive that Muhammad was indeed impotent. So these young women were condemned to spinsterhood for the rest of their lives.
http://www.annaqed.com/en/content/show.aspx?aid=16096