What I understood is that Yuki's mother raised him inside the apartment they lived in and send Rou (the brother) to live with Omi (I don't know why, I guess Yuki seemed more human as a child and Rou was more of a wolf(?))
Both of them are chimeras. But Rou's transformation is complete (we see that in both oneshots)
I believe that Rou is completely devoted to Omi. He lives only for him, so he doesn't care about any other person or beast, and that is the same with Yuki .. at least it should be, but he helps Yuki at the end, so he shows that he actually cares about his brother.
There are many things that make sense but I don't like. I believe the story takes place during a war between beasts and humans, and Omi hopes that the brothers can make a difference in the future -becauze they are chimeras but have a human form as opposed to other chimeras who always have animal traits in them. So they will act like a sort of mediator between the two sides. Or something.
I still don't like all the violence and seemingly pointless killing in both sides. I understand it's a war for territory (?) But I would like the seme to be more compassionate... I don't know, something doesn't feel right about him killing just because he has fun doing it...
Overall, I liked it! I love this author
you haave to read http://www.mangago.me/read-manga/sense_of_loyalty/ and http://www.mangago.me/read-manga/oath_of_allegiance/
=)