Late last century Richard Williams, the unbelievably clever man with zero tennis background who shaped 20 Grand Slam singles titles, suddenly up and said that among his two ball-mauling daughters, the younger would become the better.
That sounded loopy because the elder, Venus Williams, already majored in towering promise, reaching the 1997 US Open final at 17 and appearing with multitudinous hair beads on the cover of the American magazine Sports Illustrated.
Then it sounded prophetic because the younger, Serena Williams, suddenly up and won the 1999 US Open at 17 through four three-set fights with bright lights plus one final win over the same Martina Hingis who edged out Venus in the semi-finals.
Then it sounded suspect because Venus won four grand slam singles titles in 2000 and 2001.
Then it sounded prophetic because Serena won the next six for a 7-4 lead among them, and the world yet again caught up to Richard Williams' thinking.
Then, for just a little wrinkle there, it sounded almost questionable again. Venus won Wimbledon in 2005, 2007 and 2008, the last over Serena in a straight-set final, and drew within 8-7 as the 2008 US Open approached and the two played a sterling yet largely overlooked quarter-final.
Venus, brilliant through her first four rounds, had 10 set points in that quarter-final.
She served for sets at 5-4 and 5-3. She led the first-set tiebreaker 6-4, the second-set tiebreaker 6-3.
A 16-shot rally in the second-set tiebreaker contained such power and speed and bedazzlement that the New York audience stood just afterward. Yet Serena won that match, 7-6 (6), 7-6 (7). In a one-night testament to her pluck, she clambered from all that inconvenience and converted the only two set points she had.
Noting the quality of the match, she said, "I mean, I feel like I should have won a trophy now." She did anyway, two matches on.
Venus had won 34 straight sets across three Wimbledons before Serena beat her in two in the 2009 final. From there, both faced scary medical issues. Both had layoffs.
But Serena sprinkled in enough wins that when she walks out for the final today as a No 6 seed against the illness-ridden No 3-seeded final debutante Agnieszka Radwanska of Poland.
As she aims to become the first woman over 30 to win a Grand Slam since Martina Navratilova at Wimbledon in 1990, she will bring along a serve that has become a late-career talking point.
With its gorgeous, fluid motion, that serve has dug her out of three-set thorns against Zheng Jie and Yaroslava Shvedova.
It has marched her through defending champion Petra Kvitova and Australian Open champion Victoria Azarenka, the latter with a 24th ace on match point to close a taut, 8-6 second-set tiebreaker.
It has made everyone agree that it has improved with age. The USA Today's Douglas Robson listened to her parents tell how the serve just flowed more naturally from the get-go than did Venus' (even as that one proved mighty as well).
Robson tallied that in Serena's first set against Azarenka, she won 20 of 24 points while serving, and that overall she has won a foreboding 92 per cent of her services games, and that in six matches she has 85 aces and six double faults.
That was 85 aces and six double faults.
From the stands, Venus looks on with the envy long since depleted.
She has become a 32-year-old woman of steep grace.
Only 11 women have won more grand slam singles titles than her seven, so you are a lunkhead if you call her anything but a soaring success, but Serena's furnace-like will has established the order within, proved Richard astute yet again. The beloved American writer/broadcaster Bud Collins once asked Venus if that original pronouncement hurt her.
"No," she answered. "He was doing his job. You know, he was like dad and coach and promoter. So the thing everyone was always saying, 'There's never been two siblings who were great. It's not even possible for her to be great.' Obviously, he didn't believe that. None of us did."