Happy Together (1999)

The premise is so similar that one may think Ugly Alert is inspired from Happy together. There are some differences in story but a lot more similarities. The OSTs are also good in both dramas.

Both about step siblings,
in both- the father is a thug,
in both- parents die and siblings from the mothers side blame the step father,
in both- prosecutor younger brother
in both- both brothers like the same girl at one point

- siblings story
But it realtes to step siblings and their everyone goes to their own path ofc in last episodes they reunited one by one try it out!
It's not very similar but ofc u won't regert