Lead couple with 2nd guy who causes problems for them

Are there any where the male and female leads are already a couple (married/dating) at the beginning or become one early on. Then a 2nd guy comes in and causes problems for their relationship. Not to the point where the female lead actually cheats, but maybe she befriends the guy, he falls for her, and then she gets into misunderstandings with the male lead or something. This causes problems, maybe a break up. At no point though does she like the other guy. They reconcile in the end.

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