It seems Priscilla Chan indeed grew up in a working class environment: (Another link said her father came to US as a refugee from Vietnam.)
– I read the following from Business Insider, I think.
“Chan grew up in what she has described as a disadvantaged family in Quincy, Massachusetts. Her Chinese-Vietnamese immigrant parents worked eighteen hours a day, and her grandparents took care of her. Chan was the first in her immediate family to go to college, and credited public-school teachers with encouraging her to reach for Harvard. While there, she volunteered five days a week at two housing projects in Dorchester, helping children with academic and social challenges. She had since become a pediatrician, caring for underserved children.”
In the past year, this couple donated $75 millions to a SF public hospital where she was trained not a long time ago. This hospital had such a “luck” to train a resident like her.
Also, it seems they mostly donated money to organizations which serve the poor. (e.g., “Silicon Valley Community” something.)