Louis Tomlinson's Sister Félicité Dead After Suffering Heart Attack

Louis Tomlinson's teenage sister has died after suffering a heart attack on Wednesday at her studio apartment in London. Someone in the apartment called for an ambulance ... but after paramedics tried to revive her, she was pronounced dead at the scene. 

Félicité reportedly had absolutely no warning signs and they knew of no prior history of heart trouble.  She did, however, suffer from sciatica.

Back in January, Félicité posted on social media she had stopped drinking and stopped smoking cigarettes. 

Louis and Félicité were extremely close, regularly seeing each other when he was in London. 

Félicité was a fashion designer and had more than 1 million followers on Instagram. It's apparent from her Insta, she was heavy into fitness. She was planning to publish a book of her own poetry. 

She was one of 7 siblings; Louis is the oldest.

Louis has just pulled out of a performance on a BBC charity show, Comic Relief. The show was scheduled to air Friday night, but Louis obviously had to back out.  

The One Direction singer lost his mother to cancer in December 2016 when she was only 43. He recently released a song called "Two of Us," about him and his mom. The lyrics include, "You'll never know how much I miss you/the day that they took you/I wish it was me instead."