Brian Brooks is the brother of Nia Brooks.
Brian's sister, Nia, was one of the first women to graduate Ranger school. Shawn Sullivan, a friend of hers, encouraged Nia to come to Anderson/Vaughan Investigations for help when she started receiving death threats from someone who was unhappy that a woman was now an Army Ranger. She'd reported it to her commanding officer, but nothing had come of it. Alice and Valerie told her they'd find out who was behind it. Nia told them that once they found who did it, she'd take care of it herself.
Evan Connors, who had washed out of Ranger school, was suspected of sending her death threats, so Danny went to investigate him. However, Nia showed up at the bar where Evan was drinking to confront him. Brian was also at the bar and he and Danny both tried to get her to stop, but she brushed them off. Evan denied having stolen her dog tags and putting a bullet hole in them, but said he was a fan of whomever it was. He also said that she'd only gotten into the Rangers because Sergeant Moore was told he had to graduate at least one woman. When Evan said that Nia would die as soon as she got overseas anyway, Danny punched him.
Danny took Nia back to her house, which had been broken into. Someone erected a battlefield cross in the middle of the room. Danny knew it couldn't have been Evan because he'd been tailing Evan all day. When Danny and Alice went back to Nia's house and found her there with Todd Walker, who had helped her clean up and took the trash bags away in his car.
Danny took take out to Nia's place and they ended up sleeping together. The next morning, Sophie called and told him that Sergeant Moore had promoted Todd six months early. They told Nia, but she didn't believe Todd could be the culprit. In order to figure out if she was right, they had her tell Todd about going to AVI for help, which was not allowed for members of the military. They knew he'd call the person he was taking orders from. They were shocked when Brian showed up. He claimed he was trying to protect her. There were Rangers who hated her because she was a woman and didn't have her back and them not having her back in combat means she's going to die. She told him that a Ranger was all she ever wanted to be.
His father is an Army Ranger, which inspired both Brian and his sister, Nia, to serve. When Nia got into the Army Rangers, he started sending her death threats trying to scare her out, afraid she'd die in combat.
He worked with Todd Walker to send Nia death threats in an attempt to scare her out of the Army Rangers.
He is a Ranger in the US Army.