Kris Jenner, 59, Stuns in Sexy Bikini on Kardashian Family Vacation to the Caribbean

Brian Prahl/Splash News

It’s getting harder to keep up with Kris Jenner.

The momager, 59, is giving her daughters a run for their money in new photos from the family’s trip to St. Barts last week. Jenner – a grandmother of four! – showed off her enviable body in an itty-bitty black bikini and sheer loose cover-up while walking along the beach.

“After I have a coffee, I get myself to the gym in Beverly Hills, where I work out with Gunnar Peterson,” Jenner said of her 5 a.m. exercise routine in the September issue of Haute Living New York. “I end my day at 5 or 6. I used to work into the night, but learned that is unhealthy, and I wasn t feeling as productive the next day.”

Jenner and her daughters Kim Kardashian West, Kourtney Kardashian, Khloé Kardashian, Kendall Jenner and Kylie Jenner (plus Kylie’s rapper boyfriend Tyga) vacationed on the Caribbean island together, posting a barrage of sultry swimsuit selfies during their stay.

The reality stars are back in Los Angeles now, and Jenner must have been pretty wiped out from traveling: She was caught sleeping on son-in-law Kanye West‘s shoulder at Khloé’s basketball player boyfriend James Harden’s lavish yacht birthday party Tuesday.