Félicité, 18, died of a suspected heart attack.
It's a tough time for the Tomlinson family.
One Direction singer Louis Tomlinson's sister, Félicité, has died, ET has learned. She died at her home on Wednesday after a suspected heart attack. She was 18.
ET has also learned that Tomlinson was notified of the death of his sister on Wednesday night. The singer and his family are devastated at the loss of Félicité and Tomlinson has cancelled his upcoming promotional appearances while the family mourns.
Félicité was a successful influencer, with over a million Instagram followers. She revealed to fans last year that she was planning to launch a fashion line under her nickname, Fizzy.
The Metropolitan Police Service tells ET that police were called by London Ambulance Service at 12:52 p.m. on Wednesday to a residential address in Knaresborough House, SW5, following reports of a female in cardiac arrest. "Police are in the process of informing her next of kin," the Metropolitan Police tell ET. "At this stage the death is being treated as unexplained. A post-mortem examination will take place in due course. Enquiries continue."
The news comes just a little over two years after Tomlinson's mother, Johannah Deakin, died in December 2016. She was diagnosed with an aggressive form of leukemia earlier that year. Tomlinson is the oldest of her seven children; after the singer came Lottie, Félicité, and two sets of twins, Phoebe and Daisy and Ernest and Doris.
Tomlinson, 27, opened up about his mother's death during a January 2017 interview with Michael Yo on SiriusXM's Hits 1.
"It's not something that I feel 100 percent comfortable talking too much about, but just quickly, when I first found out about the news I kind of did want to throw the towel in," he said of his music career.
"But it was my mum who said to me that I've just got to keep going," he continued. "She told me very sternly that she wanted me to."
The singer -- who wrote a heartbreaking song about his mother's death called "Two of Us" -- also discussed being a father to his young son, Freddie, whom he shares with ex-girlfriend Briana Jungwirth.
"I love him, obviously, but yeah, it's affected how I am as a person, a little bit," he said. "I'd like to say it's made me a bit more mature. I don't know if that's actually true."
See more on Tomlinson in the video below.