Liam Payne also sent well wishes, posting a lengthy message to his bandmate via Twitter.
"Louis, I'm so sorry for you my brother," he tweeted. "My heart aches for you, just know I love you the same from a million miles away as I do right next to you. I'm always here for you through everything as you have been for me."
"My thoughts and prayers are with you and your family at this incredibly sad time," he continued. "I can't begin to imagine what you are all going through. RIP Johanna, you are forever in my thoughts."
Payne's girlfriend, Cheryl Cole, echoed his sentiments. "@Louis_Tomlinson my heart breaks for you," she shared. "I am so sorry. My thoughts are with you and your loved ones at this incredibly tragic time."
@Louis_Tomlinson my heart breaks for you. I am so sorry. My thoughts are with you and your loved ones at this incredibly tragic time.
ET previously reported that Deakin died on Wednesday after being diagnosed with an aggressive form of leukemia earlier this year. She was 43. In addition to Tomlinson, she's survived by six other children, as well as her husband, Dan Deakin, and grandson (Tomlinson's only son with ex Briana Jungwirth), Freddie.
"Johannah was first and foremost a truly amazing mother to seven children -- Louis, Lottie, Félicité, and two sets of twins, Phoebe and Daisy and Ernest and Doris -- whose individual talents and success are testament to the principles and beliefs she instilled in them," Deakin's husband said in a statement to ET on Friday. "She was also an incredibly proud grandmother to Freddie."
"Incredibly selfless, she would always look to put other people before herself," the statement continued. "She desired nothing more than for everyone around her to be happy and loving. She worked tirelessly on numerous charity campaigns, creating memories for many individuals and their families. It wasn't uncommon for Johannah to hear through the media of an individual in need of assistance, and she would immediately make it her objective to get that person what they often desperately needed, and rarely without success. These are the things that made Johannah happy and content in life, and all of which for me made her simply the perfect wife and best friend to face each day with. I thoroughly loved walking through life with her, and though five years was far too short a time, during that time we had so many lifetimes worth of happiness, adventures, and memories."