In Rus 1:4 it says that Naomi's two sons married to Moabite women, Orpah and Rus. We know that Rus married Machlon (4:10) the older brother and Orpah, Rus's sister (Rus Rabba 2:9) married Kilyon. Why then does it list Orpah before Rus?
Furthermore, I realize that it is possible that Kilyon and Orpah married earlier than Machlon and Rus. However, I have found no source which says so, and it would seem that standard practice was to marry off the older sibling before the younger (bereshis 29:26).