Patrick Mouratoglou showed his support for Serena Williams' sister, Venus, on Twitter on Monday as she advances at the Western & Southern Open in Ohio, leaving fans wondering if he's trying to tighten his relationship with his rumored girlfriend's family.

"#Venus playing much better now. More consistent and aggressive. In control of the rallies," the French tennis coach posted on Monday.

The tennis couple also made headlines for their relationship with Serena Williams' father, Richard Williams.

Richard Williams boycotted attending the Wimbledon 2013 tournament, where Serena Williams had an early dismissal, because he isn't happy she's dating Patrick Mouratoglou - the most likely cause of his discontent lies in the French coach's marital status, AOL Entertainment reports.

Patrick Mouratoglou is in a divorce case with ex-wife Clarisse Mouratoglou and is still dating Serena Williams.

In the first night session match, 37th-ranked Venus Williams lost the first three games before roaring back for a 6-4, 6-1 win over qualifier Jana Cepelova, Yahoo! Sports reports.