Days of Heaven (1978) on Netflix

It's 1916. Because of an altercation he has with his mill foreman, Bill, a laborer, decides to leave his home base of Chicago, and become an itinerant farm worker along with his girlfriend, Abby, and his young teen sister, Linda. Bill and Abby tell those that they meet that they are siblings if only because of the poor optics of them traveling together without being married. They head to the panhandle of Texas, where they end up working on a large wheat farm. The wealthy but sickly farmer is immediately attracted to Abby, falls in love with her and wants to marry her. Bill encourages her to marry him if only because he expects the farmer to die soon, and they would then be able to live off his wealth. Abby goes along with Bill's scheme and marries the farmer. This arrangement could have dire consequences if the true nature of Bill and Abby's relationship is discovered, and/or if Bill's Chicago past catches up with him. But a few unexpected issues arise which may further alter the on the surface harmony that exists between the three.