Kourtney Kardashian rushed to defend her younger sister Kim after she came under fire for the bikini snap she chose to post to mark her sibling's birthday.The SKIMS mogul, 42, took to Instagram on Thursday to mark Kourtney's 45h birthday but the bikini photo she shared of her posing with Kourtney and Khloe in the ocean left fans divided. In the controversial snap, the three sisters could be seen wearing matching black bikinis during their recent sun-soaked getaway to Turks and Caicos.