Ever since Wal-Mart heir John T. Walton died 10 years ago in a plane crash, it’s been widely assumed that he passed the bulk of his vast estate to his widow, Christy.

Turns out that was very wrong.

In what’s been a closely guarded family secret, Walton gave half of his then-$17 billion estimated fortune to charitable trusts and a third to their only child, Lukas Walton, now 29, an analysis of court documents reveals. Christy got the rest.

The filings, unsealed by a Wyoming court at Bloomberg News’s request, mean that Christy’s fortune as previously calculated has taken a big hit -- from $32 billion before the court records were unsealed to about $5 billion now. She’s unlikely to ever again reach her former designation as America’s richest woman, which she held until last month.

But her loss is Lukas’s gain. Though little-known outside of a few scattered social media posts, he becomes the 103rd-richest person in the world, with about $11 billion, according to the Bloomberg Billionaires Index.

That makes the grandson of Wal-Mart founder Sam Walton $5.5 billion richer than his 66-year-old mother, and wealthier than Eric Schmidt and John Paulson.

The Waltons declined to comment for this article. “Lukas Walton is an entrepreneur involved in a variety of investment and philanthropic activities,” Kiki McLean, a spokeswoman for the Walton family, said in an e-mail.

Key Vote

John Walton, the second of four children of Sam and Helen Walton, left an estate that included gold bars, a catamaran and $100 million in cash, according to the documents. Most valuable was his 20 percent interest in Walton Enterprises LLC, the family’s main investment entity.

As a result of that holding, Lukas may wield a key vote in the closely held entity, which together with another family trust controls a 50.2 percent stake in Wal-Mart Stores Inc. At more than $100 billion, the Waltons -- siblings Jim, Rob and Alice, as well as Lukas and Christy -- can claim one of the world’s largest family fortunes, according to the index.

"There’s no other public company of this size that I am aware of where a family has such a big stake," said Brian Yarbrough, a consumer research analyst at Edward Jones in St. Louis.