Like A Hero. The Invictus Chronicles, #1

Courage can be costly. Orphaned brothers Vincent and Dennis Villanueva learn the truth of those words when they create a masked crime fighter and turn him loose on Los Angeles. The brainchild of fourteen-year-old Dennis and embodied in twenty-one-year-old Vincent, "Invictus" hits the streets to jumpstart apathetic Angelenos into taking a more active role in their city. But reality isn't a comic book.
Vincent finds poverty, homelessness, drug addiction, abuse, and cast-off children. Labeled a vigilante and criminal, the shy grad student with formidable martial arts talent and abysmal people skills soon doubts his ability to make an impact. Forced to straddle an ambiguous line between moral and legal, he becomes disheartened and secretive, hiding the truth of what he's doing from Dennis and driving a wedge between them.
Feeling neglected, Dennis infiltrates a dangerous drug ring to show Vincent he can be just as heroic, not knowing that the woman in charge is weaving an insidious plot against Invictus as part of her citywide scheme of vengeance. In a race against time, Vincent must regain Dennis's trust before the brother he loves is lost to him forever.