Kendall Jenner and Kylie Jenner had a bikini showdown Sunday as they both posted sexy bikini photographs on their Instagram accounts. After the sisters spent Saturday supporting their friend Cara Delevingne at the Los Angeles premiere of her latest film “Paper Towns,” it appears the sisters spent Sunday lounging by a pool.

Kendall showed off her supermodel body and washboard abs in an orange two-piece bikini. In the photo, she sat by the pool’s edge and tinkered with her necklace. She accessorized with a pair of reflector sunglasses, and she slicked back her hair.

Meanwhile, Kylie posted her own bikini picture. She wore a black cutout one-piece suit that showed off some major cleavage.

The rivalry between the two youngest girls in the family featured in the reality-television series “Keeping Up with the Kardashians” is also being highlighted in a recently released campaign by the French fashion house Balmain. Last week, Kylie shared a photo from the campaign. In it, the sisters are covered from head to toe in Balmain creations as they appear to be attempting to wrestle each other to the ground. Kylie captioned the shot, “Sister Rivalry.”

Despite depictions of a rivalry between the two Jenner girls, Kendall and Kylie actually get along well. They just released their latest collaboration with the fashion brand PacSun, and they have had many other business collaborations.

Meanwhile, Kylie revealed in Season 10 of “Keeping Up with the Kardashians” that she believes Kim Kardashian is the family member who’s being extracompetitive. In one episode, she shared her concerns with eldest half sister Kourtney Kardashian. Kylie said she felt Kim has been hijacking her style ideas -- and doing everything better.

In that episode, both girls did photo shoots, with Kylie feeling Kim borrowed her idea of using a desert location. Kourtney told her youngest half sister that Kim has always been competitive but that she should take it in stride and feel proud her older sister thinks her ideas are good enough to imitate.