WIMBLEDON, England — Richard Williams refuses to watch his daughters Venus and Serena play each other. Says he simply can’t bear to see it, no matter the setting, no matter the stage.

So once again, the patriarch of the greatest sister act in tennis history is heading home to the United States before the Wimbledon final. That’s because the women’s singles championship at the All England Club is Venus Williams vs. Serena Williams for the second year in a row and fourth time overall.

The way the sisters won in Thursday’s semifinals could hardly have been more different.

‘‘Serena nearly gave me a heart attack,’’ Dad said. ‘‘Venus played as if she had some place to go, and she was in a major league hurry to get a great dinner.’’

Serena went on Centre Court first and came within a point of losing to Beijing Olympics gold medalist Elena Dementieva before grunting and grinding her way to a 6-7 (4), 7-5, 8-6 victory that lasted 2 hours, 49 minutes — longer than any Wimbledon women’s semifinal or final on record.

‘‘Definitely one of my more dramatic victories,’’ said Serena, who walloped a tournament-high 20 aces. ‘‘I felt like I was down pretty much the whole match.’’

Venus followed and dominated the No. 1-ranked woman, Dinara Safina, in an astonishingly easy 6-1, 6-0 win that took merely 51 minutes and equaled the most lopsided semifinal result here over the last 74 years.

‘‘The score just showed my level of play,’’ the third-seeded Venus said. ‘‘I was just dictating on every point.’’