A version of this article first appeared in CNBC’s Inside Wealth newsletter with Robert Frank, a weekly guide to the high-net-worth investor and consumer. Sign up to receive future editions, straight to your inbox.

When Peter Buffett learned that he and his siblings would be in charge of giving away the fortunes of their father, Warren Buffett, his response was clear.

“I did not want it,” Peter Buffett told CNBC. “I called him up and said, ‘I want to opt out.’ He said, ‘I don’t blame you.’ It obviously puts an enormous amount of pressure on us.”

In 2024, Warren Buffett announced that after his death, his fortune would be directed to a new charitable foundation overseen by his three children, Susan A. (Susie) Buffett, Howard G. (Howie) Buffett and Peter Buffett. The 95-year-old’s wealth is now estimated at more than $150 billion, according to Bloomberg.

Adding to the challenge, the legendary investor requested that all the money be given away within 10 years of his death. Another catch: All three must unanimously agree on how to disburse the funds.

The magnitude of Buffett’s wealth means his children will need to give away at least $15 billion a year, which would equal about 4% of annual charitable giving in America, according to data from Giving USA through 2024. The amounts are likely to increase even further with time, as Buffett’s fortune continues to grow.

“It’s something nobody has done, certainly not as a family,” Howie Buffett said.

Adds Susie Buffett: “It’s just so much money.”

The bequest has suddenly thrown the low-profile Buffett children into the spotlight. After Warren Buffett’s death, Susie, Howie and Peter will become three of the most important philanthropists in the world, scrutinized by the media, widely followed by other wealthy donors and barraged with requests for funds.

In a rare interview with CNBC’s Becky Quick, the three Buffett heirs said their world view, priorities and approach to philanthropy began in the Buffett household. While their father’s wealth was starting to grow, the children lived a middle-class or upper-middle-class life. They took the bus to public school every day. They did chores for an allowance and had jobs.

Warren Buffett drove a blue Volkswagen bug when they were growing up, they said. Their mom, Susan T. Buffett, volunteered for various groups and hosted exchange students from around the world. When Susie Buffett was in elementary school, she recalls she had to fill out a census form listing her father’s occupation and her mother told her to write “security analyst.”

“I thought he checked burglar alarms,” Susie Buffett said.

As they went on to form their own families and find their own causes, the Buffett children grew as philanthropists. Since 2006, the longtime Berkshire Hathaway CEO has given shares of the firm to each of the three children’s foundations every year, giving them each more than 20 years of philanthropic experience.

Susie Buffett lives in Omaha, Nebraska, and focuses on early childhood education and social justice, through the Susan Thompson Buffett Foundation and the Sherwood Foundation. Howie Buffett, who lives in Illinois and heads the Howard G. Buffett Foundation, devotes more of his time and resources overseas, working on food security and conflict resolution. Peter Buffett, who lives in upstate New York and leads the NoVo Foundation, works on health and economic programs for women and children. 

Warren Buffett hasn’t given the siblings explicit instructions for the money, they say. His only guidance is that it be used for those “less fortunate,” Peter Buffett said. In his 2024 Thanksgiving letter, Warren Buffett explained his confidence in giving them so much money and such wide discretion.

“I know the three well and trust them completely,” he wrote. “The 2006-2024 period gave me the chance to observe each of my children in action and they have learned much about large-scale philanthropy and human behavior. They enjoy being comfortable financially, but they are not preoccupied with wealth. Their mother, from whom they learned these values, would be very proud of them. As am I.”

Susie, Howie and Peter will likely each focus on different causes, while also funding some joint efforts. The requirement that all disbursements be unanimous is both a challenge and blessing, they say, since each sibling can blame one another if they don’t want to fund a cause.

“It makes it really easy to say no,” Susie Buffett said. “It’s like, ‘I’m sorry, I’d like to do it, but my brothers would hate it. So call them.'”

As the Buffetts prepare for a historic giving campaign, here are five principles and strategies they say they’ve leaned about effective use of capital and philanthropy: