Niall Horan has teased there is a "little bit of a story" behind Liam Payne and Cheryl Fernandez-Versini's relationship. Fans were stunned when it was revealed earlier this year the One Direction hunk had begun romancing the 'I Don't Care' hitmaker - who was a judge on 'The X Factor' when the group were put together in 2010 - after her split from second husband Jean-Bernard Fernandez-Versini, and the 'History' singer's bandmate couldn't be happier for them. Niall told Britain's HELLO! magazine: "There's a little bit of a story behind it but I won't be telling you that. "She's a great girl, really fun. He's a top man and one of my best friends. "She seems happy, he's happy, so I'm happy for them." It was recently claimed Liam, 23, is keen to "prove he's worthy" of Cheryl, despite being nine years younger than her. A source said: "Liam has fallen hard for Cheryl. "At first, he was overwhelmed by all the drama - especially her divorce - but after everything they've been through, he's so head over heels in love with her and he's being very protective. "He's always trying to please Cheryl and trying to prove to her that he's worthy of being her boyfriend, in the sense that he's so young and was always afraid that she might not take him seriously. "He's always showering her with gifts, acting like a loved-up puppy dog and planning their future together." However, Cheryl's mother, Joan Callaghan, has warned the 'Fight For This Love' singer - who was also previously married to Ashley Cole - not to rush into another serious relationship. The source said: "Her mum Joan has sat her down and told her to take things slow, and that if something is right, it will wait. "Cheryl is a real romantic at heart, but at the same time, she needs to be sure about what she's getting into. "She's already been married twice and rushed it with JB, and I think everyone is hoping she won't do that again, even though Liam is a really good guy. "She can blow hot and cold on the subject of their future together and that could be confusing to Liam."