I'm thinking that the two men might have been in a very bad, somewhat spiteful relationship with each other before the barbarian women came into their lives. Maybe the two men fighting over the same girl and during a village raid all they can do it bicker and fight with each other instead of defending the village. Then the barbarian woman saw an opportunity to gain two docile lovers, if they would only get along. TL;DR: After a bunch of sex, angst, and crying, they eventually become happy.