Two of the world's top models, Gigi and Bella Hadid, confirmed their family had been keeping a secret. The sisters revealed they have a younger half-sibling, after their father had a relationship with another woman more than 20 years ago.

Meanwhile, actress Mariska Hargitay also recently shared a family secret she'd been keeping for decades - the man who raised her was not her biological father.

Family life involves many complexities and tangles. So, why do families keep secrets? And what makes people finally reveal the truth?