Louis Tomlinson’s sister Felicite has died at the age of 18.
In a statement, the London Ambulance Service said: “We were called at 12.51pm.
“We sent two ambulance crews, a single responder in a car and an advanced paramedic to the scene.
“Sadly, despite efforts of our medics, a person died.”
Police said officers attended a southwest London residence after being called by the ambulance at 12.52am following reports of a female in cardiac arrest.
The female, believed to be aged 18, was pronounced dead at the scene.
At this stage the death is being treated as unexplained and a post-mortem is due to take place.