Kourtney Kardashian is proving that getting older doesn't require retiring that sexy bikini. After recently reuniting with her former flame Justin Bieber, the "Keeping Up With The Kardashians "(KUWTK) star decided to take a vacation. But is there trouble in paradise, with rumors that Kourtney banned her baby daddy from the trip?

Kourtney Kardashian wows in bikini

At 37, Kourtney Kardashian looks better than ever, reported Us Weekly. Turning to Instagram to flaunt her sleek physique, the reality TV diva sported a tiny bikini top and minimal bikini bottom.

“Island Ting,” wrote Kardashian for the caption, for which she let her perfectly straight locks flow loose. The mother of three youngsters, Kourtney posed in a way that revealed she's kept up with her famously strict diet and fitness regimen.

Kourtney Kardashian sparks split rumors

But while Kourtney looked healthy and fit in her photo, Scott Disick has been up to his old party boy ways, according to In Touch, which questioned whether Kardashian and Disick are headed for a split. Although Kourtney Kardashian and Scott are parents to three little children (Mason, Penelope, and Reign), Scott is "in the doghouse," according to a source cited by In Touch.

Scott reportedly was seen having some flirty fun with a beautiful brunette at the Sundance film festival, and Kourtney subsequently "disinvited him" from the vacation after the news about his flirtation, said the insider.

Kourtney Kardashian pregnant for the fourth time?

Kourtney Kardashian and Scott Disick were together for nine years before breaking up in July 2015. They subsequently reunited, and now In Touch claims that there is a paternity scandal because the reality TV star allegedly is pregnant with her fourth baby.

But the question of the baby daddy of that rumored fourth child remains unanswered.

In addition to Scott, Kourtney has been dating Justin Bieber and Younes Bendjima.

"When she told pals a few weeks ago that she missed her period and fears she’s pregnant — she also said she didn’t know who the father is," an insider told In Touch. "Kourtney is very fertile. She has a big problem."

As for how Scott reacted to the news of Kardashian's new boyfriend, Disick "hit the roof when he heard she was hooking up with Younes," added the insider.

Justin Bieber as baby daddy?

However, in July last year, Life & Style claimed that Kourtney Kardashian was pregnant with her fourth child and that Justin Bieber might be the baby daddy. The report came in the wake of Kourtney's and Justin's reunion.

“Justin would love to have a child with her," an insider told Life & Style. "They even used to joke about co-parenting a mini Bieber.”