Marvin described the Irish heartthrob as his "brother" and said the 20-year-old star will even be popping round to his house this weekend for a roast dinner!
Marvin, who rose to fame with JLS on The X Factor in 2008, explained how he has given Niall advice on his career, as both acts have found success through the talent show.
Speaking to The Mirror, Marvin said: "He's a great guy and I bonded with him from the start when he was on X Factor. He came to ask me for advice at the beginning and it's amazing to see One Direction go on to do incredible things."
One Direction are now on a well-deserved break after wrapping up their mammoth 'Take Me Home Tour' in Japan on Sunday (3 November). The boys will be back on the road next year for their follow-up tour, 'Where We Are.'
Marvin, who welcomed baby daughter Alaia-Mai on 20 May with wife and The Saturdays star Rochelle Humes, said the couple have taken Niall under their wing.
"You forget how young they are with the massive success and exposure they've had," said Marvin. "If he can draw from mine and Rochelle's experience that's great."
We know Niall is a regular visitor at the Humes' household, and back in August, Marvin and Rochelle jokingly gave Niall the night feed!
Marvin, who said that Niall is "great" with six-month-old Alaia-Mai, added: "He'll be round at the weekend for a roast dinner. We're like his big brother and sister with his family mostly in Ireland."
Watch the music video for One Direction's new single, 'Story of My Life' below: