Mark Zuckerberg and his wife Priscilla Chan on Tuesday announced the birth of their daughter, Max, and it turns out fatherhood is making the Facebook CEO feel especially giving.

In a letter to their newborn daughter, the couple made the surprising announcement that they will donate 99 percent of their Facebook shares during their lives to causes that help "advance human potential and promote quality for all children in the next generation." The duo has also formed a new organization, dubbed the Chan Zuckerberg Initiative, to help with that goal.

"Our initial areas of focus will be personalized learning, curing disease, connecting people, and building strong communities," Zuckerberg and Chan wrote in the note.

The donation currently amounts to about $45 billion, which the couple called "a small contribution compared to all the resources and talents of those already working on these issues." Zuckerberg promised more details about the effort in the coming weeks.

As for what the immediate future holds, Zuckerberg will be taking a two-month paternity leave to settle into a new family rhythm with his wife and new daughter. But don't expect him to forget about the social network now that he's taken on this new humanitarian mission — and become a dad.

"I will continue to serve as Facebook's CEO for many, many years to come, but these issues are too important to wait until you or we are older to begin this work," Zuckerberg wrote. "By starting at a young age, we hope to see compounding benefits throughout our lives."

The move is not entirely surprising. In 2010, Zuckerberg joined Bill Gates and Warren Buffet in pledging at least half of his wealth to charity. The Giving Pledge, founded by Gates and Buffet, is a "moral commitment" by America's wealthiest families to donate at least half of their wealth to charity sometime during their life or post mortem.