The Walton family, who own about 54% of retail giant Wal-Mart, continue to be the wealthiest family in the US for a second straight year with a combined fortune of about $149bn (£95bn, €134bn), according to Forbes.

However, the fortune of six heirs of Wal-Mart founders Sam Walton and James "Bud" Walton declined from $152bn in 2014, due to a decline in the shares of Wal-Mart. The fortune is held by Sam's three living children and daughter-in-law, and Bud's two daughters.

Second on the list were the Koch family with a net worth of $86bn. Koch Industries, led by siblings David and Charles, is a diversified conglomerate with more than $100bn in sales.

The Mars family comes in at number three, with a fortune of $80bn. Siblings Forrest Jr, Jacqueline and John own 100% of Mars, the largest candy company in the world with $33bn in sales.

The Cargill-MacMillan family and the Cox family come in at number four and five with $45bn and $34.5bn fortunes, respectively.

The Cargill-MacMillan family wealth was shared by an estimated 23 members, including 14 billionaires. They own 88% of agribusiness giant Cargill Inc, America's largest private company, with $128bn in yearly revenues.

The Cox fortune is shared by three family members who own Cox Enterprises, a company that deals with cable TV, broadband, newspapers, TV and radio stations.

The top 10 richest American families are mentioned in the list below:

1Walton$149Wal-Mart (Retail)
2Koch$86bnKoch Industries (conglomerate)
3Mars$80bnMars (candy)
4Cargill-MacMillan$45bnCargill Inc. (agribusiness)
5Cox$34.5bnCox Enterprises (media)
6Hearst$32bnHearst Corp (media)
7Pritzker$30bnHyatt Hotels (hospitality)
8S.C. Johnson$28.8bnS.C. Johnson (consumer chemicals)
9(Edward) Johnson$26bnFidelity (mutual funds)
10Duncan$22.4bnEnterprise Products Partners (oil and gas pipeline)