Steven is born in December 1989; his mother is Cindy Beale and his father is Simon Wicks. Cindy is married to Ian Beale and she convinces him that he is Steven's father. Simon becomes Steven's godfather, despite knowing that he is his biological father. Cindy tells Ian the truth when she and Simon reconcile. They leave Walford with Steven in December 1990; however, Ian and Cindy reconcile in 1992, and Ian raises Steven as his son. In December 1993, Steven becomes a half-brother when his sister Lucy Beale and brother Peter Beale are born to Ian and Cindy. Unhappy in her marriage, Cindy hires a hitman to kill Ian in 1996, and when this fails, she snatches Steven and Peter and flees to Italy. In 1997, Ian tracks her, Steven and Peter down and kidnaps them back. Cindy fights for custody and wins, but on the day she reclaims Steven, Lucy and Peter, she is arrested when the hitman confesses to the attempted murder of Ian and Ian gains custody of Steven, Lucy and Peter. She dies in childbirth in prison in November 1998. Steven alone attends her funeral.
Steven then grows up with various different stepmothers, and though he grows close to them all, he feels abandoned when they leave. When Ian prepares to marry Laura Dunn, Steven is anxious that they too will end up splitting; his fears are realised when he catches Ian kissing Janine Butcher in 2002. From being a quiet, sensitive boy, Steven starts rebelling and skipping school. When Laura finds out, she confronts Steven, who reveals that Ian had kissed Janine. The subsequent rows have a negative effect on Steven; he becomes angry with the world and starts writing poison pen letters to people. Ian eventually finds out and confronts Steven. Following an argument, Steven goes to his room and overhears Ian calling him "Cindy's little brat!"; Ian is forced to tell Steven that he is not his natural father. Distressed and angry, Steven decides to leave Walford to meet Simon, who lives in New Zealand.
In September 2007, Steven returns and begins stalking Ian, pretending to be Ian's late wife, Cindy. He lures Ian to an empty block of flats, and takes him hostage. Arriving back in Walford, he spends time reminiscing with Peter and Lucy, though Ian's new wife Jane Beale is initially wary of him, especially when he attempts to kiss her. When Steven's grandmother Pat Butcher tells him that Ian always considers Steven his first born, blood related or not, Steven starts to regret what he has done. Wanting to confide in his sister, Steven takes Lucy to the flat where Ian is being held. Horrified, Lucy escapes and contacts Jane, while Ian confronts Steven about the reasons for his actions. Steven tells Ian that he blames him for his mother's imprisonment and death. He is angry that Ian had not retrieved him from New Zealand; living with his biological father had not been a happy experience, and he had ended up feeling rejected and in the way.
Steven then tries to commit suicide with a gun that Lucy gives him to dispose of. Ian, Jane and Lucy try to stop him, a struggle ensues, and Jane is accidentally shot in the stomach; as a result, she is unable to have children. Ian admits Steven to a psychiatric hospital. When released, Steven goes off his medication. He tries to apologise to Jane and Ian, but finds them hostile. Hoping he will leave Walford, Ian humiliates and rejects Steven several times, going as far as to break a snow globe he had given to Steven when he was young right in front of him. Once again depressed, Steven tries to commit suicide by dousing himself in petrol; however, Stacey Slater stops him from setting fire to himself. When Ian discovers what Steven has been planning to do, he reconciles with him. Displeased, Jane fights against Steven being part of her family, but eventually relents and in January 2008, she agrees to let Steven move into the Beales' home; however, she makes it clear that she is waiting for him to mess up so he will be gone from her life for good.
Steven and Stacey grow closer in early 2008, as he supports her through the breakdown of her marriage. Steven is attracted to Stacey. She initially rejects his advances, but eventually agrees to date him. Their relationship progresses, until Steven decides that he is ready to lose his virginity, but their attempt at consummation ends in disaster when Steven can not perform sexually. Embarrassed, Steven pretends that he had lost his virginity; however, Jane's brother Christian Clarke realises he is lying and publicly announces it, leaving Steven humiliated. Steven confronts Christian and, after releasing his pent-up anger and frustration, he spontaneously kisses Christian. Realising Steven is gay, Christian tries to make Steven face up to his sexuality. Steven maintains that he is heterosexual, and successfully has sex with Stacey, but their relationship soon ends when Christian tells Stacey that Steven had kissed him.
Distraught, Steven propositions Christian, but is rejected. In revenge, Steven tells Ian that Christian had tried to seduce him. Ian is furious until Jane discovers the truth, leading Steven to confess that he is gay. Steven is grateful when Ian proves supportive, as his biological father had not been. Ian is full of praise for Steven; however, he does not realise that Steven has been hiding his runaway daughter, Lucy. Steven does not want to share Ian's attention, so he makes plans for Lucy to flee to France; however, Pat discovers his plan and is hit by a car as she is trying to apprehend him. Pat is hospitalised, and in order to stop her from telling Ian about Lucy, Steven tries to smother her with a pillow. Pat wakes up, but Steven continues in his murder attempt until Ian interrupts him. When Pat tells Ian about Lucy, Steven tries to deny it, but Ian sees through his lies. He traces Steven to St Pancras railway station, and discovers him with Lucy. Steven has booked her a ticket on the Eurostar, but Ian persuades her not to go and Steven flees. Later, back in Walford, Ian spots Steven spying on Lucy. Ian confronts him, admitting that he is glad that Steven is not his biological son; he tells him that if he ever returns to Albert Square, he will kill him. Devastated, Steven heads to the tube station and leaves Walford. In 2014, Peter reveals that Steven was living in New Zealand with his father, Simon. Peter and fiancée Lauren Branning leave Walford for New Zealand to join Steven in February 2015.
In May 2016, Steven returns with Lauren and Louie after they learn that Jane is in hospital after being attacked by Bobby Beale, who also confessed to killing Lucy. Ian initially rejects Steven, but Steven says he is back to help and repair any damage he made in the past. Ian accepts Steven's offer of driving him to the hospital. Steven and Lauren do not tell anyone that they are together but when Ian finds out, he throws them out. Ian eventually accepts Steven back into the family but Jane is wary of him. Steven helps Ian at his restaurant and impresses him with his sales skills. Sadly, Jane soon finds an unfinished credit card application in Lucy's name and accuses Steven. Steven admits being responsible because he realised Ian is struggling financially. Ian promotes Steven to restaurant manager. When the restaurant is burgled, it is revealed that Steven arranged it and sold the kitchen equipment to pay debts. Kyle Slater, an employee at the restaurant, realises Steven arranged the burglary, so Steven sends him on a training course, and he admits to Lauren what he did. Later, Kyle asks Steven for a pay rise, saying he has kept quiet about the burglary, but Steven refuses.
Steven worries when Jane asks to look at the restaurant's accounts as he has stolen money. He makes excuses not to let her use the restaurant's laptop and tells Lauren he will fake some invoices. Steven is overjoyed when Louie says his first word, "mama", and gets him to say "dada", filming it to show Lauren. However, she sends the video to Peter, upsetting Steven as he tells Lauren that he sees himself as Louie's father but Lauren says Peter will always be Louie's father. Steven also worries that Lauren never says she loves him when he says it to her. When Jane looks at the restaurant's accounts and realizes payments are being made to a fake company, she knows it can only be Ian or Steven but worries about confronting the wrong person. She soon discovers that Steven set up the fake company and confronts him; he explains he borrowed the money to help Peter, who was drinking heavily and getting into fights and Lauren does not know the whole truth, so Jane tells him to be honest with her. She is angry that Steven was not honest and considers visiting Peter; Steven says he wanted to protect her and Louie, and going to New Zealand out of guilt or pity will be a mistake.
Lauren meets Josh Hemmings, a man who works in her father Max Branning's office, and they are attracted to each other. Josh encourages Lauren to apply for a job there but Steven is unimpressed by Lauren's plans as he wants her to spend more time with him and Louie. He suggests that they start trying for a baby but Lauren refuses because she wants to concentrate on her career, so Steven secretly pieces holes in condoms. Lauren gets a job at the company and tells Steven that she barely sees Josh but Steven visits her at work and sees her with Josh, and he becomes suspicious. Steven is unaware that Lauren is pregnant and planning an abortion, although her sister Abi Branning makes him question Lauren and Josh's relationship. During an argument with Abi, who resents Lauren, Steven is stunned to hear Lauren aborted his child. A few days later, following Abi's 21st birthday party, another disagreement between Abi and Steven ends with them sleeping together. Some time after, Steven has sex with Abi again after seeing footage of Lauren and Josh. Despite the affair with Abi, Steven insists he wants to be with Lauren and Abi does her best to poison his mind against her. When Lauren tells Josh that she doesn't love Steven, Abi persuades her to return to New Zealand. Just as she is about to leave, Josh visits Steven and tells him that Lauren has resigned from her job. Steven bashes his head against the wall, causing it to bleed. He later bumps into Lauren before she leaves and she plans to end their relationship, but notices Steven's head injury. In a desperate act to keep Lauren with him, Steven lies the injury is caused by him trying to remove a brain tumour, claiming that he has cancer and he is dying.
Although Abi discovers the truth, she decides not to tell Lauren after Steven tells her he is planning to leave Lauren to be with her. However, Steven tells Lauren he wants to adopt Louie and stuns Abi by proposing marriage to Lauren in The Queen Vic. When Lauren leaves Walford to visit Tanya, conflicted on her relationship with Steven, Max tells him he knows he lied about the brain tumour and gives him an ultimatum: help him move some clients from his property or he will tell Lauren the truth. Max tells Steven to set fire to the flat while making sure the clients safely exit the premises. Steven refuses and tells Max that he will tell Lauren the truth when she returns and tells Abi that their affair was a mistake. However, when Lauren texts to say that she will be staying with Tanya for longer, Steven agrees to Max's plan. However, the plan appears to backfire when the residents hear sirens of fire engines, police cars and ambulances. Max finds Steven in The Vic alleyway and Steven tells him he does not know if the clients exited the flat. Max tells Steven that he is on his own as he drove Ian's car to the flat, while dismissing Steven's claim that if he goes to prison, Max will go down too. Max tells him to find an alibi, so Steven asks Abi. Steven tells Max that he has an alibi and mentions that the clients did exit the flat. Jane later discovers Max's revenge plan and Steven's brain tumour lie and Max convinces Steven that Jane is trying to get rid of him. Steven confronts Jane and blames her for Max's behaviour, but Jane tries to reason with Steven and reveals Abi is pregnant. However, Steven refuses to believe her, and after berating her about framing Max for Lucy's murder, sets fire to the restaurant, and leaves Jane to perish in the flames.
Believing Lauren trapped inside, Steven and Max run back into the inferno and Steven saves Abi, who became trapped upon finding, and attempting to save Jane. Max tried to get Steven to kill Jane but he refuses and tries to save her. Max violently shoves him into a countertop, causing Steven to be rushed to hospital where he tells Abi that he loves her and will try to make their relationship work. He then suffers a cardiac arrest and dies from his injuries. When Steven's lies are revealed, it is also revealed that Steven died of injuries to the liver and so only Abi attends his funeral and reads a eulogy dedicated to him. Abi then has Steven cremated and hides his ashes away from Lauren when they visit their mother Tanya Branning in Exeter. However, Lauren eventually discovers the truth after finding Abi in her wedding dress. Horrified by what she has learned, Lauren tries to flush Steven's ashes down the toilet, but Abi stops her, eventually telling her the truth about her pregnancy with his baby. In December 2017, Abi and Lauren learn about their father's scheme before discovering his knowledge over the former's pregnancy with Steven's baby. They eventually find out on Christmas that year the truth about Steven's death when their mother Tanya reveals that Max killed him – causing them to disown their father, who subsequently gets into a fight with Ian when he and his mother Kathy learn the truth as well; the latter then explains this to Phil, who then confronts and attacks Max. Shortly afterwards, Abi and Lauren fall from the Queen Vic roof; both survive and are taken to hospital, where an ultrasound shows Abi and Steven's baby is alive. Fearing that Abi may go into cardiac arrest following her devastating diagnosis of brain stem death, the doctors decide to deliver the baby via cesarean section. Soon after, the doctors switch off Abi's life support when it becomes clear that the chances of reviving her are impossible.
A year later, many people blamed Bobby for Max's revenge including the deaths of Steven and his own daughter Abi.