Harry Styles' parents miss their son.

The 'Best Song Ever' singer and his One Direction bandmates - Liam Payne, Zayn Malik, Louis Tomlinson and Niall Horan - have achieved global stardom since appearing on 'The X Factor' UK three years ago and although Harry's mum and dad are thrilled their son is so successful they do wish they could see more of him.

Dad Des Styles and mum Anne Cox - who married her long-term partner Robin Twist in June, with Harry acting as best man - revealed their feelings in intimate interviews which feature in the band's 3D documentary film ''One Direction: This is Us'' - which had its world premiere on Tuesday (20.08.13).

Des said: ''Harry went as a kid to 'The X Factor' and never came home.''

Anne also admitted she worries her 19-year-old son's success could be short-lived.

She said: ''[The fame could] come crashing down. There is always this feeling you have to be ready to pick up the pieces and we've been waiting to - but it just gets bigger and bigger.''

Liam Payne's father also became emotional during a scene in the film when he explained how much he has missed his son since he entered Simon Cowell's talent show aged just 16.

Geoff Payne said: ''He's the only lad in the family and now that's gone I'll never get it back.

The group were all in attendance for the 'One Direction: This is Us' premiere in London's Leicester Square last night (20.08.13) where they were greeted by thousands of screaming fans - some of which had camped outside two days prior get a prime spot to see their idols.

Liam - who is also joined in the band by Zayn Malik, Louis Tomlinson and Niall Horan - admitted it was difficult for him to watch his father's confessional in the documentary.

The 19-year-old star said:''He's always so happy when I see him. To actually see what he's like when I'm not there was a bit mad.''

After signing autographs and taking photos with fans, the boys moved onto private members' club Soho House when the premiere ended to celebrate.