Johannah Deakin has passed after a long battle with leukemia.
"It is with immeasurable sadness that Johannah Deakin's family said goodbye to Johannah in the early hours of Wednesday 7th December 2016," a statement from her family reads.
"Earlier this year Johannah was diagnosed with a very aggressive form of leukaemia that required immediate and continuous treatment. We respectfully request that the family are given time and space to grieve in private."
In addition to Louis, Deakin leaves behind six other children, Lottie, 18, Felicité, 16, twins Daisy and Phoebe, 12, and twins Ernest and Doris, 2, whom she gave birth to in 2014.
Some of the One Direction boys took to social media to share their best wishes:
Our thoughts go out to Louis and his family xx