From their choice in men and hobbies off the court to who is the better singer, the Chan sisters - Yung-jan and Hao-ching - disagree on practically everything.
The former likes actor Eddie Peng's smouldering looks while the latter prefers South Korean actor Lee Min Ho. But the one thing they are unanimous about is that their doubles partnership has been a smashing success so far.
With three titles this year - doubling their total as a team to six - the Taiwanese are the second-most prolific siblings in WTA history, trailing only Venus and Serena Williams' haul of 21 trophies.
Yet, their biggest triumph could come this week as the third seeds target their maiden WTA Finals crown. It is a fair possibility after their one-sided 6-2, 6-2 rout yesterday of second seeds and double Grand Slam winners Bethanie Mattek-Sands and Lucie Safarova.
Said Yung-jan, 26 and the older sibling by four years: "It was a much tougher match than it looked but we definitely played very well, and everything clicked for us."
Blood may be thicker than water but the on-court chemistry displayed in Singapore by the sisters took time to develop.
I'm not the older sister on the court... she never listens to me.
CHAN YUNG-JAN, Older sibling
Yung-jan - who is 1.7m and stockier than her lanky 1.75m sister - was a fairly successful singles player, reaching a career high of world No. 50 in June 2007 but made her name in doubles. She has 14 WTA doubles titles and was thrice a losing Grand Slam doubles finalist.
They experimented as a partnership in 2011 but had to wait two years before they tasted victory.
"We have very different personalities and could not work as a team," said Hao-ching whose modest singles career peaked at No. 1,097 in April 2013.
But the goal of winning a medal at next year's Olympics in Rio stirred them to keep trying.
NO RUNNING AWAY
She bakes all day and forces me to eat her new cakes.
There are no egos when they walk out together to compete now, only two girls with a sense of humour, evident by their constant teasing of each other during the 10-minute interview.
"I'm not the older sister on the court and definitely not the leader because she never listens to me," said Yung-jan with a grin.
It also helps that they do not bring their work home with them.
"Outside of practice and matches, we almost never talk about tennis. That's the job of our dad (who is their coach). He's the only one who wants to discuss tactics, not us," said Yung-jan.
Left to their own devices, the game takes a backseat to other interests like baking and singing.
"She bakes all day and forces me to eat her new cakes," said Hao-ching. "At least they're good!" comes the reply, a not-so-subtle dig at Hao-ching's warbling.
So far, they are hitting the right notes at the Singapore Indoor Stadium. With two wins in the bag, they top the White group and are on course to advance to the knockout rounds, where they are likely to meet top seeds Martina Hingis and Sania Mirza.
The world No. 1 pair have won eight events this season, including Wimbledon and the US Open, and hold a 4-1 record over the Chans.
Said Yung-jan: "They're the team to beat but we have beaten them (in Cincinnati in August) and that gives us the confidence."
The signs so far suggest everything is working well in tandem. Just do not expect them to reach a consensus about their ideal man.