Bloodline by Joe Jiménez

In his junior year, seventeen-year-old Abraham learns how to drive a stick shift. He falls in love for the first time. And he has been in three fights and suspended twice, all before Thanksgiving. His grandmother and her girlfriend, the ones who have raised him, fear for his life and the hard future that awaits him. "He needs a father," his grandmother says. "He needs a man. I can't do this, Becky. We can't. Not on our own."

Soon, his Uncle Claudiothe son with a fat police file who has hurt his mother so many timesis back in the house. Determined to make a man of his nephew, he takes the boy to the gym and shows him how to use free weights and become bigger and stronger. Meanwhile, Abraham's feelings for his friend Ophelia grow, and she tries to understand why he fights. "This will end badly," she warns. "Nothing good can come from this." 

At school, Abraham learns about genetics, and he wonders if people are born bad. Is it in their DNA?