A 77-year-old woman who lives a quiet life in Texas has been identified as the fourth richest woman in America worth an estimated 12.2 billion dollars.
Elaine Tettemer Marshall's wealth had previously escaped attention because of her discreet lifestyle, despite the fact she is also the daughter-in-law of the late Anna Nicole Smith.
Peter Newcomb, the editor of the Americas section of the Bloomberg News’ Billionaire Index, discovered her massive fortune after researching who owned the minority share in Koch Industries, the second-largest closely-held company in the US.
Mr Newcomb and his colleague, Matthew Miller, knew most of the company was owned by brothers Charles and David Koch but found 15 percent had belonged to a man named E. Pierce Marshall.
When Mr Marshall died in 2006, he passed on his valuable stake in the company to his wife Elaine.
Despite their wealth, Mr and Mrs Marshall managed to avoid almost all publicity, even though Mr Marshall's father was J. Howard Marshall — the man who, in 1994, married 26-year-old Anna Nicole Smith when he was 89.
Smith then technically became mother-in-law to Mr and Mrs Marshall.
After years of fighting between Smith and the Marshall family after J. Howard Marshall’s death in 1995, the Playboy model was left with nothing.
Ultimately, it was Mrs Marshall who received a huge share of the wealth.
Her fortune now puts her behind the two Walmart heiresses, Alice and Christy Walton, and confectionary company beneficiary Jacqueline Mars.
After media reports of her fortune emerged this week, Mrs Marshall said the valuation was "ridiculous".
"I just go on living my life," she said through her spokesman David Marguiles.
"This is ridiculous, but it doesn't affect me or affect how I live. I will continue to live my life as I always have."