"Happy birthday Mum. I love you x," the former One Direction singer wrote.
Deakin died at the age of 43 in December 2016 after battling leukemia. In a statement to Us Weekly, Johannah's husband, Dan Deakin, said she "was diagnosed with a very aggressive form" of the cancer earlier in the year and "required immediate and continuous treatment."
"It's not something that I feel 100 percent comfortable talking too much about, but just quickly, when I first found out about the news, I did want to throw the towel in," Tomlinson, 25, said of Johannah's death during a SiriusXM interview in January. "But it was my mum who said to me that I've got to keep going. She told me very sternly that she wanted me to."
Three days after her death, the British singer debuted his collaboration with Steve Aoki, "Just Hold On," on The X Factor. He was in tears at the end of the performance, prompting judge Simon Cowell to applaud his bravery.
"I've known you now for six years [and] what you've just done, and the bravery, I respect you as an artist, I respect you as a person," Cowell, 57, said at the time. "Your mum was so proud of you, Louis, and she was so looking forward to tonight. She's looking down on you now. She's so proud."
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