The 'Live While We're Young' hitmakers remained coy when probed as to which of them is most likely to get hitched, but they think Irish singer Niall could surprise them with an accidental proposal.
Louis Tomlinson - who is dating model Eleanor Calder - said: "I would love it to be Niall.
"You know when Niall says things that he doesn't really mean and he just comes out with them? Imagine him doing that: 'Will you marry me? S**te! I didn't mean to ask her that.'"
"Imagine we just go away, have a year apart, doing whatever, all doing different things and come back and Niall's just got married. I can see that happening."
Bandmate Harry Styles insisted he is happily single, but if one of them were to settle down he'd pick Liam Payne.
He said: "I think it will be Liam because when he likes someone, he really likes someone."
Liam wasn't so keen on the idea, however, as he has just split from his long-term partner Danielle Peazer.
He suggested that Zayn Malik - dating Little Mix singer Perrie Edwads - is the most likely of the five members to elope.
Liam joked: "I reckon Zayn will do it spur of the moment."
Niall added: "Zayn would get married in Vegas."