One Direction's Harry Styles has joked about having Arnold Schwarzenegger as a father-in-law after meeting his daughter Katherine.

The singer, who turns 18 today, got to know the 22-year-old after she watched one of the band's music videos - she then met the band in Los Angeles, where they shot scenes for an episode of Nickelodeon sitcom iCarly.

"Katherine's been in the studio watching us. Imagine having Arnie as your dad-in-law," he told The Sun.

Katherine - the eldest child of Terminator star Arnold and Maria Shriver - previously tweeted: "Just watched my first One Direction video w(ith) my cousin and @Harry_Styles is a cutie indeed!"

Harry admitted he and bandmates Zayn Malik, Niall Horan, Liam Payne and Louis Tomlinson have resorted to some extreme measures to avoid the crowds of US fans waiting around to catch a glimpse of the boyband.

"We have had to use the hotel service lift. There are girls in the main lift the whole day, just going up and down hoping to bump into us," he said.

The group, who are currently in the States doing some promotional work, will have roles in an upcoming episode of iCarly alongside lead actress Miranda Cosgrove.