Gigi and Bella Hadid come from a blended family, with their father, Mohamed Hadid, being a proud father of five.
Yet in a bombshell statement, the supermodels revealed that they have welcomed another sister into their family following their dad's "brief romance" with a woman named Terri Hatfield Dull in 2001.
Secret sister
Gigi and Bella spoke to the Daily Mail on Thursday about the family addition - 23-year-old fashion designer Aydan Nix.
"Over 20 years ago, our dad, while single, had a brief relationship that led to a pregnancy," they began.
"Aydan was born and raised in Florida, growing up with the man she lovingly knew as her father until his sudden passing when she was 19."
"After his passing, she decided to take a genetic test out of curiosity, and that's how she discovered a biological connection to us," they continued.
The Victoria's Secret stars added that they "first connected in late 2023" with their sister, and "embraced Aydan with open arms".
"We've cherished this unexpected and beautiful addition to our family," they shared. Aydan recently graduated from the Parsons School of Design in Manhattan, and she shares a slew of striking features with her sisters like tanned skin and sharp cheekbones.
"As siblings, we've had many open and loving conversations - with Aydan included - about how to support and protect her," Gigi and Bella continued.
"Aydan and her family value their privacy, and we fully respect that. We kindly ask others to do the same and honor her wish and right to her anonymity as she continues her life as a young woman in New York."
A blended family
Mohamed, a luxury real estate developer, was married to Gigi and Bella's mother, Yolanda Hadid, from 1994 until they split in 2000. They also welcomed a son together, Anwar, who is a model just like his sisters.
The trio have two half-siblings from Mohamed's previous marriage to Mary Butler: Marielle Hadid, 44, and Alana Hadid, 39.
Marielle is a successful businesswoman and founded Living Well with Marielle, with services like closet organization and floral design classes on offer.
She co-founded a sunglasses brand with Alana, who works as a fashion designer.
Alana opened up about how close she is with her siblings in a candid interview with Grazia in 2019, and shared how fame has not changed their relationships at all.
"We are really protective and supportive of each other," she said. "We love each other, we want to be close, and we've never thought anything of each other apart from that we're brothers and sisters - that's why we remain so close."
She continued: "Regardless of Gigi and Bella's fame, and how hard they've worked, we really are just sisters. We go shopping, we do a little cooking, we have a group chat. We do all the things that sisters do."
Alana shared that there was no competition between the siblings, and they all loved and supported each other equally.
"I'm not in competition with my sisters or brother," she explained. "We all have an innate work ethic and I feel successful - I do a lot of things that people perhaps don't know about, as do my sisters. Being famous is not being a success."
To learn more about Gigi and Bella's mother Yolanda, watch below...