When I was a kid I saw a movie in which a boy dies cut by a combine harvester. This is a love story that presents two sisters who are in love with the same boy . The biggest sister has a relation with this boy and the smallest secretly loves him. Both of them are blondes, as far as I remember. There is a scene in wich the lovers swim in a small lake I think. This is all I remember. Can anyone identify this movie from this one scene?

I believe you're thinking of "The Man In The Moon" with young Reese Witherspoon.