But you're not alone if you have no idea who they are and why and how they got so famous.
And since they don't seem to be going away anytime soon, we've put together this quick primer:
Posing in matching lingerie and furs on the latest cover of V — their first magazine cover together — the sisters almost look like twins, but they're not. They are actually a year apart. Gigi is 19 and Bella is 18, and they have a 16-year-old brother, Anwar.
Their mother, who divorced their father in 2000 and is now married to composer David Foster, describes them this way: Bella is the brunette who prefers to wear all black. Gigi is the blonde and bubbly "girl next door."
Different personalities mean they have different tastes in men.
Asked by V if they've ever fought over a potential love interest, Bella said, "No, never. We would never touch the same person."
Gigi chimed in, "We don't have the same type."
Gigi has been linked on-and-off to Australian singer Cody Simpson for over a year, but is currently rumored to be dating Joe Jonas. Meanwhile Bella is reportedly dating Canadian singer-songwriter The Weeknd (real name Abel Tesfaye).
Bella seemed to confirm that she was dating The Weeknd after posting to Instagram a photo of her sister kissing the musician on the cheek after presenting him with the Artist of the Year award at the 2015 Much Music Video Awards in Toronto earlier this week.
Gigi also posted a shot of herself with the musician, calling him "my brother."
The sisters share some of the same famous friends but also spend time with different pals.
"She put something like twenty successful women in the industry in her video," Gigi told V. "I felt so lucky to do that because I felt like it was really a sign of our collective willingness to support each other and have each other's backs and kind of hold hands along the way."
Bella is nipping at her older sister's stilettos. Also signed to IMG, she has appeared in spreads for Teen Vogue and Elle UK. She also joined Bella on the runway of the Tom Ford Fall/Winter 2015 show and was most recently named the face of Botkier's spring 2015 campaign.
Both support themselves and are enrolled in school in New York -- Gigi at the New School and Bella at Parsons School of Design.
And both share a work ethic.
"What I've been doing a lot every day is I have three goals: be kind, work hard and make a friend," Gigi told V. "When I do those little things on set every day, those are the things that then lead to creating relationships and building opportunities. Because you don't know who those people are gonna go have dinner with and talk to that night."
Bella echoed her older sister. "No matter if they're working next to you, below you, or above you, be kind and generous to everyone you meet," she told V. "Yeah, it's bizarre because it's weird for people to be nice these days."