Wimbledon, England ? Nobody can truly imagine what Venus and Serena Williams are going through as they prepare to face each other in their third All-in-the-Family Wimbledon final this afternoon. How does one fathom what it feels like to grow up in the same room as your sister, spend your entire life loving and admiring her, and then have to compete against her on your sport’s biggest stage with a $1.5 million check on the line?

The Williamses are used to it. It is the seventh time the Palm Beach Gardens, Fla., sisters have met in a Grand Slam final, and the fourth time at Wimbledon. For the seventh time in eight years, a Williams will win the championship.

Mike Bryan is one of the rare people with an inkling what goes on in the Williamses’ psyche. He and his twin brother, Bob, are the world’s top-ranked doubles team. They don’t play each other in singles anymore, but back in the day, they did.

It was always awkward, and never great tennis. In fact, their parents didn’t let them play against each other until they were 16 years old and mature enough to deal with it. When they did reach finals, one brother or the other would default.

“I remember the times we played, we were both kind of flat,” Mike Bryan said. “You want to win, but you don’t want to beat your brother. You’d feel really bad if you’re beating up on him and look over and he’s hanging his head. There wasn’t a lot of emotion either way because you feel like once you’re both there, your family’s already won. I’ve watched every Williams final, and it looks like they’re a little flat, which I understand.

“I mean, no matter who wins between Venus and Serena, they’re going to have dinner together that night and fly home together.”

That’s exactly what they did in 2003, the last time the Williams sisters faced each other in the Wimbledon final. Younger sister Serena won for the second year in a row, and the family celebrated at Benihana in London.

This time, the sisters are sharing a rented home and planned to eat breakfast together before their much-anticipated match. A few hours after the singles final, they will be partners for the women’s doubles final. In 2002, Serena beat Venus for the singles title, and then the siblings won the doubles title. “I don’t think a lot of players could imagine what we go through because most players never have a sibling that’s a world-class athlete in the same sport,” she said. “They’d want to see their sibling do well, go all the way to the final, and do well – until she plays you, obviously. At this point, it’s every Williams for herself.”

But, Serena said, “Once we shake hands at the net, we’re sisters again.”

The Williams sisters are not the first siblings to compete for a Wimbledon women’s title. The first Wimbledon women’s final in 1884 was between Maud and Lillian Watson, who played in white corsets and petticoats. Maud beat her older sister 6-8, 6-3, 6-3.

No sisters but the Williams have played each other in any Grand Slam final in at least 40 years. Other sports have famous siblings. NFL quarterbacks Peyton and Eli Manning both won Super Bowls. Phil and Tony Esposito were hockey stars. Leon and Michael Spinks won Olympic gold boxing medals. And Roberto and Sandy Alomar were Major League Baseball stars.

But rarely have siblings competed against each other one-on-one. Skiers Phil and Steve Mahre did at the 1984 Olympics, with Phil edging Steve for the gold, but it almost never happens. ESPN analyst Patrick McEnroe can “somewhat relate” to the Williamses’ dilemma. He is the younger brother of former No. 1 John McEnroe. They played in one tour final in Chicago in 1991, and little brother won, 3-6, 6-2, 6-4.

“I was at the prime of my career, John was at the tail end of his, so for at least at that moment, we were somewhat equal,” Patrick said. “I stress somewhat. Usually, he’d kill me.

“I remember a quandary of emotion. I didn’t really desperately want to beat him, but my brother desperately wanted to beat me because I was so much younger than him and to lose to me would have been the ultimate embarrassment.”