Two billionaire daughters reach US Open semifinals. Here’s where their money comes from.

The two American women who reached the semifinals of the US Open not only share their perseverance and skills, but they have something else in common: their fathers are both billionaires.

On Thursday, US-based Women’s Tennis Association (WTA) No. 12 Emma Navarro will face Belarusian No. 2 Aryna Sabalenka for a spot in the final. On the other side of the draw, US-based No. 6 Jessica Pegula will play Czech Karolina Muchova.

It is no secret that the Navarro and Pegula family are wealthy. Pegula previously told Agence France Presse that she finds it “irritating” when assumptions are made about her based on her father’s business success.

“I did something in the media recently. They said, ‘What’s the most annoying thing?'” she told the outlet. “That people think I have a butler, that I get chauffeured around. I have a private limousine, that I fly everywhere privately. I’m not like that at all.”

She also admitted that she “finds it kind of funny, because I don’t really know anyone who lives like that. It’s outrageous.”

Where did their fathers’ wealth come from?

Terry Pegula, Jessica’s father, made his fortune in oil and gas as the founder of East Resources. In 2010, he sold most of the company’s assets to Royal Dutch Shell for $4.7 billion, Forbes reported. He now oversees a sports empire that includes ownership of the Buffalo Bills and Buffalo Sabres.

According to Forbes, Terry Pegula is worth $7.7 billion.

Navarro also has financial resources that are separate from her earnings on the professional tennis circuit. Her father, Ben Navarro, is the founder and CEO of Sherman Financial Group. According to Forbes, he is worth an estimated $1.5 billion.

The financial services company buys and services consumer debt from financial institutions, credit card companies and retailers. Navarro also owns the Charleston Open, a WTA Tour event.

Tennis can be prohibitively expensive, with court, equipment and tuition costs adding up and often creating barriers for many young players. While both of the American semifinalists may have had access to top-notch coaching at a young age, no amount of money can buy a US Open championship.

—With reporting from the Associated Press