See Aisha, Al-shafi'l, Al-Zuhri all claims pregnancy can go upto 2 to 4 years. Why are they claiming like this?
I will tell that... Before that we need to see some other references.
Hamza is also uncle of Muhammad.So this uncle Hamza of Muhammad is just 4 years older than Muhammad.
Now when we look at Muhammad's parents you can get information about it on same book on page 1 & 2.