SINGAPORE — They used to “fight all the time” as siblings, but now Chan Yung-jan and Chan Hao-ching are standing shoulder to shoulder fighting against the world’s best women’s tennis players.

The sisters from Chinese Taipei started pairing up only in June, but they are fast establishing themselves as the next big thing in the women’s doubles arena.

Yesterday, at the BNP Paribas WTA Finals Singapore, they dispatched two-time Grand Slam-winning pair of Lucie Safavora and Bethanie Mattek-Sands 6-2, 6-2 for their second win here. They had earlier beaten Caroline Garcia and Katrina Srebotnik 6-4, 7-6 on Sunday.

It adds to the scalps the Chan sisters had claimed over the past three months, which include current world No 1 doubles pair of Martina Hingis and Sania Mirza at August’s Cincinnati Masters, as well as and former top seeds Sara Errani and Flavia Pennetta in June’s Aegon International.

The recent upturn in performances and results have given them the confidence that they — like the Williams sisters, Serena and Venus, before them — can rule the doubles game one day.

Already, they are the second most successful sisters in WTA history, with four doubles titles, behind the Williamses’ 21.

“We want to be world No 1 one day,” said the elder sibling Yung-jan, 26. “We don’t want to talk about it too much now, but yes. The recent results are showing us that we are on the right track. Tennis in Asia has improved a lot. We have seen top players emerged from this part of the world, like Li Na and Sania.”

The Chan sisters’ path to the top has been largely a family affair: Their father, Yuan-liang, is their coach, and their mother Liu Hsueh-chen is their agent.

“It definitely helped because a family knows each other well, and provides the best support,” said Yung-jan, who revealed their father was a hard taskmaster when they were young. “He knows that if we don’t work hard, we won’t have a good future.”

The Chan sisters may be siblings, but there were no shortage of growing pains as a budding doubles pair.

“Initially, if we lose two points, for example, we refused to talk to each other,” Yung-jan said of her relationship with Hao-ching, 22. “We would trade angry expressions like ‘don’t touch my hand!’ but we don’t actually say them out loud on court, but we say it with the eyes. We are aggressive and competitive like that.

“Now though, we try to give in to each other more. If there is something we are not happy about, we tell the other party to calm down, and that it is okay.” ADELENE WONG