Any dramas where the female lead loves the second male lead brother, but then falls for the male lead brother. She ends up with the male lead brother.

The only one I know of is the jdrama Suki no Hito ga Iru Koto.. but I can't think of any others atm :) Hopefully someone else will come along with more!

Slow Dance - a group of friends drama; two of them are brothers. It was a long time since I watched it but I remember liking the feeling that you couldn't tell who was going to end up with whom.

Saigo kara nibanme no koi - very good drama! (If you don't mind older main leads.)

Definitely second Weightlifting Fairy Kim Bok Joo (although I think technically they're cousins even though they live as brothers). Also:

  • Imperial Doctress (I can't remember the exact details, but I don't think the guys had the same mother and father)
  • Moon Lovers Scarlet Heart Ryeo (Although actually four of the princes / brothers like her at various points. She loves one but is betrayed by him, loves another and loves him until she dies / he loves her to the end and they have a child, but they don't marry each other, she marries a third brother for... reasons. The fourth brother dies. It's pretty messy.)