Felicite Tomlinson has tragically died aged 18.
"The love and best wishes from all of us at Comic Relief go out to Louis and his family at this bad time".
It's the second tragedy to hit the Tomlinson family in recent years.
"He spoils me and the girls and he's happiest doing that".
A statement from the Metropolitan Police Service said, "A post-mortem examination will take place in due course".
Felicite and Louis lost their mum Johannah to leukemia back in 2016.
Utah Jazz Owner Apologizes For Russell Westbrook Incident
Keisel told Salt Lake City television station KSL that he told Westbrook to "sit down and ice your knees, bro". The problem is fans sitting close to the court voicing more than just displeasure towards the actual game.
New Zealand terror attack suspect appears in court on murder charges
People caught up in the mass shootings at two mosques in New Zealand have spoken of their terror as the massacre unfolded. A witness described the sound of gunfire breaking out just as the prayer leader began his sermon at a mosque.
Monfils withdraws from Indian Wells. Thiem will play Raonic in the semifinal
Williams fought off two break points to tie the second set 2-all before Kerber again won three games in a row for a 5-2 lead. In the victory, Bencic won 78 percent of her first serve points and 45 percent of her second serve points.
The late star was well-known on social media and regularly shared posts with her 1.3 million followers on Instagram.
Her death is now being treated as "unexplained" at this stage, but it's suspected the cause of death was cardiac arrest.
Her last post was just four days ago.
Tomlinson has reportedly pulled out of a scheduled performance for British charity Comic Relief, with a source telling The Sun, "Louis is obviously distraught at the loss of his sister".
Following her death, Tomlinson released the song Just Hold On - his debut solo single - in her honour, and he performed it on the X Factor just days later.
American singer-songwriter Charlie Puth said he is sending "prayers" to Tomlinson and added: "I can't imagine how hard it is right now".