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The young heartthrob, who first stepped into the limelight as a contestant on The X Factor, will no doubt be celebrating in style. His rumoured girlfriend, Keeping Up With The Kardashians star Kendall Jenner, is said to be planning a big birthday bash with the help of Harry's close friend Nick Grimshaw. Harry and Kendall have been romantically linked since November 2013.
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"Kendall wanted the party to be in London so that Harry's friends and family could all be there," an insider reportedly told The Daily Star.
"The rest of One Direction and a whole host of other celebs will be on the guest list. It won't be a tame affair, and Kendall will pull out all the stops to make sure it's a night to remember."
Early on Saturday, Harry took to Twitter to thank fans who had donated to Believe in Magic in honour of his birthday. The charity helps seriously and terminally ill children by giving them "magical experiences" to "make their lives happier."
"Just saw donations to @believeinmagicx for my birthday. Thank you... You're all very, very kind and nice .xx," tweeted Harry to his 19.2million followers. It was no surprise that the terms #HappyBirthdayHarry and #20picturesofharryfromyourcameraroll started trending on the social media site given Harry's legion of fans.
The Worcestershire-born singer and his fellow bandmates — Zayn Malik, Louis Tomlinson, Liam Payne and Niall Horan — were put together as a group on The X Factor in 2010. The band instantly shot to fame with hits such as Kiss You and What Makes You Beautiful, but Harry also made headlines for his string of high-profile girlfriends.
Harry has been romantically linked to Caroline Flack, Taylor Swift and Cara Delevingne.