3. TharnType - Type acts drunk to confirm his suspicions.

4. Hometown Cha-Cha-Cha

24 hours have passed.

10 dramas/movies where the FL's brother and the ML are close/good friends.

1. Hwarang - They were close friends but FL brother dies.

5. My Unfamiliar family 

6. Kill Me, Heal Me 

7. Saiai

bonus : Bad Buddy - FL brother is boyfriend with the ML lol. Well, one can argue whether Love is considered FL or not 

Would a second male lead count?
9. Strong Woman Do Bong Soon (FL’s twin brother and 2nd ML the cop are close friends)

10:  I'm Not a Robot:  FL's brother is ML's assistant more than friend, but they get along well. 

Or, if that's not accepted, Homemade Love as #10.

https://mydramalist.com/24351-im-not-a-robot

https://mydramalist.com/58203-samgwang-villa-lovers

New topic:  Where ML and FL live together in an unusual house, i.e. the house is one of the distinctive parts of the drama.