Bron Studios and Indigo Films are partnering on the rom-com starring Jason Sudeikis and Rose Byrne.
Mewshaw and Van Til will make their feature screenwriting and directorial debuts on Tumbledown.
Production is set to kick off in October in Vancouver on the story of a widow who falls for a brash New York writer who barges into her rural Maine town to investigate the death of her late husband, a folk music icon.
Kristin Hahn of Indigo Films and Aaron L Gilbert [pictured] and Margot Hand of Bron Studios are producing.
Olivia Munn, Joe Manganiello, Blythe Danner, Michael McKean and Beau Bridges round out the key cast.
CAA packaged the project and represents North American rights.