Serena Williams claimed a fifth Wimbledon title on Saturday and paid an emotional tribute to big sister Venus whose career, badly affected by recent illness, is slipping into its twilight.
Serena, 30, and Venus, two years older, have won 10 of the last 13 singles titles at the All England Club.
Saturday's win over Agnieszka Radwanska took Serena to 14 Gramd Slam trophies and a new ranking of four in the world.
But in sharp contrast, Venus, whose first round defeat to Russia's Elena Vesnina on the opening day was her worst at Wimbledon since 1997, is battling to still remain a contender.
The last of Venus's 43 career titles came in Dubai in 2010 while her last Grand Slam title was in 2008.
Furthermore, she was diagnosed with the fatigue-related illness Sjogren's Syndrome last year which kept her off tour from the US Open until the Miami tournament in March this year.
Many in the sport expect Venus, now down at 58 in the world, to quit after this year's US Open and having had another shot at the Olympics, which will be held at Wimbledon.
"I don't know what I would have if Venus didn't exist. I don't even know if I would own a Grand Slam title or if I would play tennis, because we do everything together," said Serena.
"Growing up I copied Venus, everything she did. She was a real big influence for me. So when she started winning, I wanted it so bad. When she became number one I had to be number one.
"I had to work harder. I had to do everything in my power to get there. I have no idea what would happen if she wasn't around."
Serena said that just as Venus had rallied round her when she was battling life-threatening blood clots which kept her off the tour for a year, now she repays the favour.
She believes that support will be crucial when the sisters team up again in London later this month in an attempt to capture a third Olympic gold medal following wins in Sydney in 2000 and Beijing four years ago.
"I have to be more supportive. She's so strong. I can't imagine what she lives through every day. So she's an incredibly strong individual," said Serena.
"I feel like I have to be really understanding."