Jason Segel and Emily Blunt were like ''brother and sister'' while filming 'The Five-Year Engagement'.

The 32-year-old actor - who co-wrote and starred in the movie - ''knew'' he would have good onscreen chemistry with the brunette actress before they even began shooting the romantic-comedy.

He joked: ''I've often imagined what could've been with us but time played a cruel trick on us. We are like brother and sister but we got along so well that I knew we would have that kind of chemistry onscreen.''

The movie tells the story of Tom Solomon (Jason) and Violet Barnes' (Emily Blunt) five-year engagement, which sees their relationship become increasingly strained.

Emily admits she was drawn to the project because Jason - who is dating 'Dawson's Creek' beauty Michelle Williams - had written such a ''great female role'' that seemed ''funny'' and ''true to life''.

In a joint interview with Newslocal, Emily added: ''I really wanted to work with Jason again and he'd written just a great female role, just so much fun to play. I thought it was a real explanation of a relationship even though what they go through is really funny and kind of out there it just seemed true to life.''