In 1961, Donald and Mildred Othmer invested $25,000 each with Warren Buffett, by 1998 their combined fortune reached nearly $800 million

In the early 1960s, Donald and Mildred Othmer each invested $25,000 with Warren Buffett, a family friend from Omaha, Nebraska. Decades later, the couple's combined estate was valued at nearly $800 million.

Othmer was a chemical engineering professor at Polytechnic University in Brooklyn, New York. He had worked as a teacher and a buyer for her mother's clothing business. They lived in Brooklyn and were known for keeping their lives simple despite their growing wealth.

The story came to attention in July 1998, after their estates revealed the scale of their fortune and the large donations they had planned for educational institutions, hospitals and other organisations.

How did they build their fortune?

Their wealth grew through long-term investments managed by Buffett. They had known him from their hometown, where he began building his investment business.

At the time, the shares were worth $42 each, according to an Associated Press report. By the time their wealth became public, the value of Berkshire Hathaway had risen substantially.

Their fortune was estimated at around $800 million when their estates were reported in 1998. Their story became an example of how long-term investing can build wealth over several decades.

How much did they leave for charity?

The couple's estate included major gifts to universities, hospitals and cultural organisations. One of the largest donations was $190 million to Polytechnic University, where Donald had spent much of his career.

Long Island College Hospital in Brooklyn was set to receive $160 million, while the University of Nebraska-Lincoln was allocated $140 million. The Chemical Heritage Foundation in Philadelphia was due to receive $125 million.

Other beneficiaries included Planned Parenthood of New York City, the Brooklyn Historical Society and the Omaha Board of Education.

Meanwhile, their charities faced heat over the money given to Long Island College Hospital. A separate report in 2013 said the Othmers had established an endowment of about $135 million for the hospital, intended to be held permanently.

However, the hospital used a portion of the fund in transactions approved by the courts, including arrangements involving loans and other financial obligations. The issue drew criticism from people concerned about the hospital's finances and the original purpose of the donations.

In 2013, Buffett said he believed the Othmers would feel betrayed if they knew how the money had been used