Fullmetal Alchemist: Brotherhood, Rainbow: Nisha Rokubou no Shichinin Recommendations
Both plots focus on the "brotherhood". There are dark settings and suitable music for every part of the story. Both highly recommended if you like mature anime!
Both series have self reliance in common. FMA shows you the darker side of life and 2 brothers overcoming it. Then there is this series. Be warned it not for the light hearted. I was forced to drop this series after episode 2 because I could not take my heart strings being abused like that.
Deep emotions will be felt. You must be ready for them.
They teach you a lesson why familiy and friends are important, they both have some cruel scenes.