Tyler Jefferies was the son of Jed Moss and Vicky Jefferies, for a time he was the leader of a teenage gang which terrorised the residents of Coronation Street.
In early 2018, Tyler began hanging around with Simon Barlow and later introduced him into the ranks of a gang. By March 2018, the negative influence that Tyler and his gang were having on Simon's behaviour started to show as he joined them in causing havoc for the residents of Weatherfield by vandalising parked cars and being rude to his neighbours on the street.
Eventually Simon's father, Peter Barlow, discovered Simon's involvement with the gang - after he was witnessed by Roy Cropper helping to mug Audrey Roberts; an incident which left her in Weatherfield General. Feigning remorse, Simon turned on the tears when confronted by his father and admitted that while he was with the gang, it wasn't him who had mugged Audrey. While Audrey believed that he had been led astray by the gang, Simon showed little sympathy and bragged to Tyler about how he had got away with the mugging.
Tyler and his gang continued to loiter on the corner of Coronation Street. When Carla Connor advised Simon to leave the gang, Tyler became aggressive and began to threaten her to stay away. On this occasion, Carla was successful in leading Simon away from the gang. However, this had little impact and within a day, Simon had joined Tyler in throwing a brick through a car windscreen parked around the corner from the Rovers.
In April 2018, Simon continued to rebel with Tyler as the pair stole alcohol from the Corner Shop and bunked off from school, regardless of threats from his dad's girlfriend Toyah Battersby. However, the friends fell out when Simon sent a message from Tyler's phone to Summer Spellman, fooling her into thinking Tyler wanted to go out with her. Tyler was disgusted with Simon's actions and warned him to never use his phone again. Their association wasn't harmed inherently though as just a few days later Simon joined Tyler in stealing Toyah's car and going for a joyride.
The pair didn't have anything to do with each other for a couple of more months until Simon was wheeling baby Susie Price down Victoria Street and came across Tyler and two friends. Simon accepted a cigarette from Tyler which outraged Eva Price when she rounded the corner and she wheeled the infant away.
They soon got into their old ways when Tyler refused to pay Alex Warner for four cans in Roy's Rolls, but this was just a distraction to enable two of his gang mates to rifle the till of £80 which they then used to buy an expensive hoodie for Simon, saying it made the delighted lad an official member of their gang. Upon hearing of the theft, Peter dragged Simon down to the Weatherfield Police Station but no charges were laid as there were no specific evidence against him. Nevertheless the pair were barred from the cafe until further notice by Roy Cropper.
Pensioner Flora McArdle was the next person to gain Tyler's attention when Simon let slip that she had just inherited a large sum of money and would be out that afternoon at a party. Simon joined Tyler as he jemmied open the door to the corner shop flat looking for valuables. Flora returned and disturbed the pair but was put out of action when Tyler threw a jewellery box across the room at her head. Flora tried to cover for Simon but had no option to admit that he had been involved, while making excuses that he was a good lad who had just got involved with the wrong crowd. PC Mills and colleague called at No.1 and arrested Simon. At the station, they questioned the boy in Peter's presence. He realised Tyler was the other lad involved and forced his tearful son to admit the fact in front of the officers. Both Simon and Tyler were duly charged and the younger lad was threatened by the thug who said he was going to hurt him in ways he couldn't imagine if he testified against him in court.
He began by poisoning Eccles the dog with slug pellets, although the animal recovered from the attack and then put glass in a meal that Simon was eating with Leanne Battersby in Speed Daal to celebrate being given just a referral order in court. A few hours later, Tyler and another member of the gang attacked Simon in the street but he was rescued thanks to the intervention of Kate Connor.
To protect Simon, he was sent to work at Underworld on the basis of safety in numbers with the large number of staff there but Tyler was watching and saw his opportunity when he realised that the lad had been momentarily left alone in the factory. He and a mate tried to gain entry but Peter and Carla were summoned to help. In a terrifying escalation, Tyler shot Peter from the car that he was speeding away in but thankfully only with a paint gun. Nevertheless, Simon received a text saying that next time it would be a real gun.
Simon bravely gave evidence against Tyler who was given a youth rehabilitation order and imprisoned. To ensure the lad stayed off Simon's back, Peter found his mother Vicky paid employment at Natty Knicks reaching an agreement that she would keep her son and his mates in line.
This seemed to work and seemingly Tyler dropped off the radar. At some point in mid-November 2018 he was out of custody and attended a party where he and fourteen-year old Amy Barlow got chatting and ended up having sex. She got pregnant, only realising her predicament two months later. Unable to abort the child with a pill from the family planning clinic, she confessed her state to her family although she refused to name the over-age father. Both Aadi Alahan and Simon were accused of being the culprit but Amy told Simon who was responsible. She had a clandestine meeting with Tyler where he refused to accept any responsibility for his actions although he admitted he was struck by the way that she seemed to genuinely like him on the night of the party. Tyler was happy for Simon to take the rap and made Amy see him in his true colours in doing so. He even went to far as to threaten Simon again with violence should he tell anyone what he knew. He did contact the girl a few days later asking to see her but this was only to confirm she was getting an abortion and she embarrassed him in front of his mates when they realised he'd got an underage girl pregnant and they laughingly called him a "paedo".
A couple of weeks later, his mum pushed Robert Preston to employ him as a part-time pot washer in the Viaduct Bistro, saying he deserved a second chance. At the same time, she tried to integrate herself back in Amy's life, saying her son repented of his attitude and wanted to play a part in the upbringing of his child, much to the anger of Steve and Tracy McDonald who wanted to adopt their own grandchild and were keen to keep Tyler out of their daughter's life as much as possible. Tracy went so far as to try and bribe the lad with £5,000 and threaten him with a pair of secateurs but old habits die hard and he threw away the chance of any money by winding Tracy up when the opportunity presented itself. He later admitted to Tracy that despite his mother's wishes, he wanted nothing to do with his own child.
Tired of all the pressure she was being put under, Amy had an abortion without informing anyone else concerned but inevitably the secret came out. Tracy informed Vicky of the news and the blamed her for creating the pressure. The row escalated into a fight in the middle of the street which Tyler had to break up. Tired of the trouble that seemed to follow him around, Michelle Connor forced Robert to sack him. Two weeks later, Tyler was getting in trouble again and Vicky pleaded with Robert for another chance. He was unable to take him on himself but he did arrange for a friend in Macclesfield to employ him in his cafe as a kitchen hand.
Robert later began a relationship with Vicky, while estranged from Michelle and was a regular visitor at the household. When Robert reunited with Michelle he broke off his relationship with Vicky, unaware that she was pregnant. When Tyler discovered both of these facts he found Robert outside the bistro and punched him for abandoning his pregnant mother. After Vicky gave birth to Tyler's brother Sonny Jefferies, and Robert would also be accidentally shot dead on Christmas Day 2019, Tyler, Vicky and the newborn Sonny moved away to Ireland.