I read this Wikipedia article on Khadija's father,Khuwaylid ibn Asad.
http://en.wikipedia.org/wiki/Khuwaylid_ibn_AsadKhuwaylid ibn Asad
Khuwaylid ibn Asad (Arabic: خويلد بن أسد) was the father of many prominent people in the very early Islamic history:
? Awwam ibn Khuwaylid
? Halah bint Khuwailid
? Khadijah bint Khuwaylid
? Hizam ibn Khuwaylid
From Banu Asad
Father:Asad ibn Abd-Al-Uzza[1]
He was a merchant, a successful businessman whose vast wealth and business talents were inherited by Khadijah and whom the latter succeeded in faring with the family's vast wealth. He died in 585 CE.
It is a common Muslim claim that Muhammad first gave women rights of inheritance, yet pre Islamic Khadija had inherited her business & wealth from her father, I was discussing this with my Muslim cousin Adil a few days back. Adil retorted that women in pre Islamic Arabia inherited only if they didn't have brothers, but Islam gave them the right of inheritance even if they had brothers(albeit, half the inheritance of their brothers! ).
But Khadija had two brothers, she still inherited so much wealth from her father, which of course she put to good use.
This proves two things:
1) Pre Islamic Arabian women inherited property from their fathers.
2) Pre Islamic Arabian women inherited property & businesses from their fathers even if they had male siblings, so the society must be giving them sufficient opportunity to succeed in business or professions, otherwise their parents wouldn't be leaving them businesses.
Although her brothers too are mentioned in Islamic sources, they aren't mentioned as particularly rich folks, leading one to speculate that her father probably thought that she was the most capable of his 4 offsprings & gave her the bulk of his business!