Did you understand the story completely? Rou is the one that contributed the most in bringing his brother and Daigou together.
If you read the manga carefully, you will notice that Rou’s purpose is to let Daigou save Yuki when Yuki is kidnapped by other organisation. Rou decided to not catch Yuki (this is the first time he goes against Omi’s order) and let Yuki get kidnapped so that Daigou and Yuki have time to talk and make up with each other.
If Rou followed Omi’s order which is to bring Yuki back to his organization, the two couldn’t confess their feelings to each other, and the story would have gone on the wrong path.
Rou also protected Yuki from the beasts of other organizations before Yuki got kidnapped.
He also approaches Daigou (in front of Yuki’s house) to make sure that his assumption about Daigou’s love for Yuki is right. He wants to ensure that Daigou loves Yuki and Daigous definitely saves Yuki from his kidnappers. If Daigou’s love for Yuki is not big enough and Daigou decided to not save Yuki, I believe that Rou will come to save his brother and bring his brother back to Omi.
Rou does care for his brother, he is just the type of person who does not want to express his feelings (Tsundere type :3).
Both Rou and Omi are good people. They want the main couple to be together and wish for their happiness.
Omi did a great job in raising his boy >.<
Sorry for the wrong name. It’s Godai my phone auto fixed the name and I didn’t notice
I kinda don't like rou, he give zero fucks about my baby yuki and he's his ACTUAL baby brother wtf