Gigi Hadid and Bella Hadid revealed that they have a younger sister, 23-year-old Aydan Nix, who they said their dad Mohamed Hadid fathered shortly after his breakup with their mom Yolanda Hadid.

Wether [sic] it was skiing, horseback riding, surfing, skating ... Lexie Moreland/WWD/Penske Media via Getty Gigi Hadid Says 'Everyone Was Freaking Out' Over Her Silver Hair — and Reveals ...