I think we are getting our wires crossed. I was talking about his much older first wife, who was a widow.
According to the most accepted tradition, Muhammad married at the age of 25 to his first wife Khadija bint Khuwaylid, who was a 40 year old widow.  She lived with him for 25 years. After her death in 619 CE, he married a total of 12 women over the remaining years of his life.
Khadijah bint Khuwaylid
At the age of 25, Muhammad wed his wealthy employer, the 40-year-old daughter of a merchant, Khadija. This marriage, his first, would be both happy and monogamous; Muhammad would rely on Khadija in many ways, until her death 25 years later. They had two sons, Qasim and Abd-Allah (nicknamed al-Ṭāhir and al-Ṭayyib respectively), both died young, and four daughters—Zaynab, Ruqaiya, Umm Kulthum and Fatimah. Shia scholars dispute the paternity of Khadija's daughters, as they view the first three of them as the daughters from previous marriages and only Fatimah as the daughter of Muhammad and Khadija. During their marriage, Khadija purchased the slave Zayd ibn Harithah, then adopted the young man as her son at Muhammad's request. Abu Talib and Khadija died in the same year. He declared the year as Aam ul-Huzn (year of sorrow).