One Direction fans have taken to Twitter to offer words of condolence to the Doncaster popstar following the news.
Louis has yet to react publicly to the news although his sister Phoebe Tomlinson confirmed it on Instagram earlier today.
She posted a photo of her granddad carrying the London 2012 torch. Alongside the photo, she wrote: “RIP grandad Keith. You were so kind Grandad!!”
Thousands of One Direction fans have posted messages of support to Louis and his family following the sad news.
@harrymoonavenue tweeted "so sad, he was always there for the fans and supported louis so much, I pray for louis and his family #RIPKeith"