A spokesman for the family confirmed that Mark Zuckerberg and Priscilla Chan sold one of their San Francisco properties for $31 million in an off-market transaction.

According to Zilllow, the transaction represents the most expensive sale in San Francisco so far this year.

Although the deal was completed on July 1, the documents have only recently been made available to the public.

The Chan Zuckerberg Initiative's vice president of operations, Na'eem Salaam, signed a grant document between the seller and the buyer on behalf of SFRP.

Mr. Zuckerberg and Ms. Chen were unavailable for comment, despite the organization's official confirming the agreement.

According to Mansion Global, they paid $53 million for almost 600 acres of land on the Hawaiian island of Kauai last March.

A few weeks after it was advertised, the price was reduced to slightly under $5 million, and it was removed from the market earlier this month. Currently, it is available to rent for $11,000 per month.

The Chan Zuckerberg Initiative was established in 2015 with the mission of "helping address some of society's biggest challenges—from eradicating cancer to enhancing education,