These three billionaires—(left to right) Abigail Johnson, Rob Walton and Julia Koch—are all among the country’s richest heirs.One of them, Rob Walton, just led a family group to bid $4.65 billion for the Denver Broncos NFL team. Here are the other heirs that rank the highest on Forbes’ list.ByAshock ran through the sporting world last week when a group led by Walmart heir Rob Walton won the bidding war for the Denver Broncos NFL team with a $4.65 billion offer. The eye-popping sum made the de...