Snowman (2003)

Although at first unwillingly, Seo Yun Wook and Han Pil Seung later become the best of sister/brother-in-law. They depend on each other for help, trouble, and fun. Seo Yun Jung, Pil Seung's wife, is grateful at the happy relationship, but things go astray when Wook grows a greater affection for Seung. When Wook confesses her feelings for Seung, the two start to grow apart. Although they later end up in the same police department, they try hard to avoid each other, and Jung starts to realize the reason why.

Cha Sung Joon is Wook's friend and the son of a rich hotel owner. Although he knows that Wook likes her brother-in-law, he never gives up his feelings for her. Things seem to turn out alright when Wook starts to date Cha and forget about Seung , but her sister Jung dies. The dangerous yet innocent love for her brother-in-law puts Wook in a terrible situation...how is love different in a family?