Last night, Kendall, 23, shocked fans by posting a steamy video of her kissing Bella while straddling her on the grass.
Friends can be heard cheering in the background as the stars lock lips.
“Happy birthday sexy,” she captioned the clip, also sharing snaps of their luxurious vacations together.
RadarOnline.com readers know that earlier this year, Kendall called things off with NBA star Ben Simmons. And before that, she was even reportedly spotted hooking up with Bella's brother, Anwar Hadid! Bella, meanwhile, recently broke up with on-and-off boyfriend The Weeknd.
While both have faced rumors about their sexuality, they’ve always laughed them off. In April 2018, Kendall told Vogue she’s simply less public about her relationships than her famous sisters.
Regardless of the speculations, fans were happy to see the longtime friends having fun in the video. Though Kendall didn’t get to spend time with her friend on her big day, Bella had fun celebrating with a family brunch at Sadelle's in New York City and a pottery painting afternoon at Color Me Mine with mother Yolanda Hadid and sister Gigi Hadid.