With Dad snapping photos from the stands, the sisters sure formed an opposing duo warming up side-by-side along the baseline. When Venus smacked an ace to end the opening game, she and Serena slapped palms.

Their interaction doesn't change much as they move closer to a possible Grand Slam final.

They are, after all, used to this: There have been seven all-Williams championship matches at majors, with Serena holding a 5-2 lead. Overall, the sisters are tied 10-10.

"We still encourage each other. I mean, on finals day, we don't say, 'You can do it!' to each other. At the same time, we're doubles partners, too, so we have to be focused on the doubles court and work as a team," Venus said. "I mean, we've got it all figured out at this point, what's coming up. So the key is for us both to do well and to get to that final."