Kylie Jenner, Kourtney Kardashian heat up Instagram with bikini posts: 'It's getting hot out here'

Sister, sister! Kylie Jenner and her older half-sister Kourtney Kardashian are both spending time soaking up some sun.

Kardashian, 41, took to Instagram on Monday to share a photo of herself -- in a black two-piece -- lying on a reclining chair outside, resting her head on her arm.

"Evolve as you please," the reality star wrote in the caption.

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Just a few hours later, Jenner, 22, shared a video on her own account, donning a similar black swimsuit.

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The video showed Jenner, also relaxing outside in the sun, spraying herself with a skincare product in slow motion.

Mary J. Blige's "Be Without You" played over the video.

"It’s getting hot out here," the makeup mogul captioned her brief video.

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The fun in the sun continued for Jenner, who shared two more selfies in the black bikini to her Instagram Story.

Kylie Jenner 

Kylie Jenner  (Kylie Jenner/Instagram)

Additionally, Jenner gave fans a glimpse into her day outside, sharing a video of herself putting on the product before a blonde pal did the same.

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The same video of Jenner was shared to her skincare line's Instagram account with the caption, "Don't forget your SPF!"