This is a pretty old one (I'm thinking prior to 2005). Also fairly short (as in single page).
My memory is that it's first person POV from the vantage of one barbarian/warrior after the day's fighting. His buddy has a pair of twins who resist as best they can (not effective at all), the narrator's catch is older and submits wholly. It may actually be from the POV of the older woman, I know it's not from the side with resistance.