Voight portrays a bad-cop role, implying that he likes to get the job done but does not care how many rules or protocols he breaks to catch the criminal(s).
Voight's unit respect him as he is often right and has earned the unit's trust. Even after being investigated by Internal Affairs multiple times.
Voight fostered Erin at the age of 13, after which he adopted her. Erin often brings up that he saved her life after taking her off the streets, and he sees her as his daughter and is very protective over her, particularly from her real mother, Bunny, who he tries to keep away from Erin. Bunny blames Voight constantly for 'taking' Erin away from her. Bunny swore she'd changed but after Erin left Intelligence and got lost after Justin's death, she offered drugs and parties and brought Erin back into the life she'd left. Erin realised this and came back, after Voight made her promise to cut ties with Bunny, which she did. However, when Bunny tells Erin that her real father, Jimmy, is here, she's surprised and happy to see that Bunny had been sending him photos of her since she was a child, which he kept lovingly. But Jay's DNA test proves he's not her father and Jimmy is angered while Erin lashes out at Bunny again. Bunny then goes to see Voight, who had told Jay that Bunny probably knew the truth, and told him that Erin should run a DNA test on him. He ignores her and she tells him that he'd like to pretend that 'that night didn't happen'. It's unclear what she's referring to and it has not been touched upon again.
Voight had a son, Justin, who unlike Erin, did not get his life straight until he had his son, Daniel. Justin was seen when Voight asked Erin to pick up after his release from prison. They had dinner afterwards, where Justin told Erin that he thought Voight loved her more than him because she was 'perfect'. However, in the season 3 finale, Justin was killed after trying to help a friend and Voight swears to avenge his death, but exactly what happens between him and the killer is not revealed.
Voight was involved with Internal Affairs (IA), who had sent him to prison in the first place. After his quick release and promotion to the head of Intelligence, IA kept a close eye on Voight and made sure that he followed their orders. Voight didn't like this as he was constantly being told how to run things and what to do. The tensions escalated when Sergeant Edwin Stilwell took charge in Different Mistakes and began to demand a partnership, and then immediately had Hank arrested after he was caught in a tough spot with another criminal. Sitwell then interrogates Voight and tells him to keep doing his work by bringing in the criminals otherwise he'll be arrested for sure. Voight is angered and takes it out on Sumner, giving her desk work as she's been assigned by Sitwell but insists that she's not working with IA. Voight thinks Sumner is working with Stilwell as he kisses her, but she doesn't like him and tells him never to try that again or she'll go to his wife.
Stillwell then gets involved with illegal work, when he tells Voight that instead of arrests, he'll be fine with getting some of the street money that Voight takes. Voight is conflicted on what to do. It's revealed that it is Jin who is working with Stillwell because he's blackmailing him about something his father has done. To maintain his cover, Sheldon shows Voight Sumner's call logs, which shows her calling Stillwell. He transfers her out without a thought and replaces her with Atwater, believing her to be working with IA, even though she wasn't. However, he figures out soon enough that Jin is the one working with Stillwell. He drives him to the edge of Chicago and tells him to get out, where he threatens him harshly.
In the season finale, Jin hurried back to the station, packing his things and phoning his father and telling him to leave town immediately. He then quickly put something in an envelope and posted it off. Amidst comforting Jay and Dawson, who were both dealing with their own upsetting family issues, Voight is called to a crime scene. It is Sheldon and he has been killed at the edge.
Jay recieved a 6 week later package containing a USB in Call it Macaroni. It's revealed it was sent by Sheldon, who attached a note saying he only trusted Jay with it. Considering that Sheldon was killed soon after, Jay isn't sure of what to do. Erin tells him to give it to Voight, but he doesn't until he sees it for himself. It supposedly has information on who killed him and since it wasn't Voight, he gave it to him. He tells him that he should give it to police, and Voight says he will take care of it. Voight goes to see Stilwell, who is revealed to be Jin's killer. He says he will give him in and Stillwell says that if he does, he'll tell everyone that Voight was working with IA and his reputation will be ruined. Voight decides to not hand the USB in, which upsets Jay when he demands for the USB back and Voight refuses.
However, Sheldon's parents come to see Voight and in their grief, they thank him for letting Sheldon be part of his team because of discrimination issues that he had dealt with in his previous jobs. This moves Voight and he realises he should hand in the USB, which he does. Stillwell is arrested and while it does not do a lot to Voight's job, Erin is upset he didn't tell her about IA. Voight then also gives Sheldon' father enough money to wipe out the debts he's been buried in and that was used to blackmail Sheldon.
Voight then met Olive Voight, who revealed she was pregnant with Justin's baby and that she needed to get in touch with him and the only way she knew to do this was through him. Voight welcomes her into the family and begins to invite her over for lunches and helps her through it. However, while getting money for her after she reveals some financial problems, he is attacked in his own home and him and Olive are kidnapped in An Honest Woman. She is nearly suffocated as the kidnappers attempt to find the combination to the safe and he gives it to them. Olive then tells Voight that she accidentally told a friend about the safe, who then threatened her and made her do this. He isn't happy until she shows him a long gash along her stomach, where they threatened to cut her if she didn't help them. He and the team eventually catch the group behind this and Justin comes home. Voight suggests that Justin get married and gives him the engagement ring that belonged to their mother.
Nadia is then murdered and this sends Erin in a downward spiral as she loses control. She is on drugs and spending her nights out and staying with Bunny, who encourages this behaviour. In Life is Fluid, Jay tracks her down and tells her that her 'grace period' is ending the next day and she needs to make the decision of either coming back or telling him she's no longer his partner. She doesn't do either and leaves. However, Jay is then taken in a undercover op gone wrong when he is made. The team is too late and the kidnappers get away, taking Jay with them. They then send a video where Jay is being beaten to Intelligence, demanding all their CI files in exchange for him. Alvin secretly calls Erin, who instantly comes back to help and answers Voight question of who will be the one to make the trade. He refuses to let her back because of what she's been doing the past weeks and is upset with her. She insists so he lets her to do it. After Jay is saved and they're back, Erin tells Voight she wants back in. Voight agrees but says she'll have to break her ties with Bunny and come live with him again if she wants to, so she agrees.
Olive, Justin and their son Daniel is seen again and they are a happy family. Justin is out of town a lot and Voight suspects he's been in shady business when he comes home and doesn't tell anyone and then gets linked to a case of a murdered woman. The team isn't sure what to think but then Justin is shot and left for dead. Voight finds him and tries to save him but he dies. This hits Voight hard, especially when they find out that the murdered woman was a friend of Justin's who needed help, and they both died because he was trying to help her out of a situation.
This deeply angered and upset Voight, who swore to avenge his death. He found the killer and took him to the edge of Chicago. It is not clear what happened next, as Erin showed up and tried to stop him from killing the man. Erin was told to leave and a gunshot was heard in the background.
In The Silos, further investigation into Voight and Erin's whereabouts on the night of Justin's death lead the police to the site where Voight had taken Justin's killer, where they excavate but find nothing. Commander Crowley is sure that Voight killed the man but the lack of evidence means she has to reinstate him. It is unclear what happened to the man or between Erin and Hank, but Erin has nightmares about shooting someone.
On the same day, Hank comes home to find Olive packing her things. He asks her where she's going and she tells him she's moving. She hands him Daniel for a few minutes and tells him she just can't stay in Chicago anymore because of what happened to Justin, so she then takes Daniel and they leave, leaving Voight upset and hurt as he asks her not to.
In Little Bit of Light, Erin is left hurt when she finds out Jay is still married to another woman. Jay leaves and goes to stay with his brother and the two ignore each other at work. Voight tells Jay he warned him about the problems of dating each other and that if they can't work it out, he'll be gone.