a wonderful trope i love!! i wish i had more to recommend but i can confidently recommend:

the one for me by ohhennyhenny: chansung brothers and minchan best friends! chan is The Over Protective brother of all time and Minho is a guy who struggles with love. Sooo fun and cute i really recommend!

growing pains by asgeir: this is technically cousin's best friend with cousins minlix. Very slice of life and sweet with a healthy side of miscommunication and pining <3