Kirsty Dorothy "Dotty" Cotton played by Molly Conlin in her initial stint from 2008 to 2010 and Milly Zero from 2019 onwards, is the daughter of Nick and Sandy, sister of Charlie and Ashley and granddaughter of Dot Branning. She is also the aunt of Matthew.
Kirsty Dorothy Cotton was born on 1 February 2001, She was the result of a sexual relationship that Nick Cotton had, with an alcoholic woman named Sandy as part of a one night stand, during early 2000, Nick met Dotty's mother Sandy, when he was staying in a squat, in North London, which the Nick and Sandy story, was never told, nor featured, during the special spin-off episode Return of Nick Cotton, but did happen sometime off-screen, between the 10 week period, which was skipped forward, through the episode, between the two events of shortly after Nick's prison release, from Blackmoor Prison, and just weeks before, the build up to when Nick saw the ghost of his late father Charlie Cotton, in the dream he had, and also, when he tracked down his son Ashley Cotton, and ex-girlfriend Zoe Newton, to reunite with his son Ashley.
On the 1 February 2001, Dotty was secretly born, whilst Nick was still living back in Walford for a while, with his mother Dot Cotton, and sometimes his son Ashley, who also came to stay, but Nick wasn't even aware, and didn't actaully know, that his daughter Dotty, even existed, until quite sometime later, way after his departure from Walford, back in June 2001, following his mother Dot, disowning him, after his son Ashley's funeral, due to the fact, that she learned, Nick was responsible of his son Ashely's death, when he tampered the breaks on Mark Fowler's motorbike, In attempt to have Mark killed, but Ashley nicked his motorbike, and got killed instead.
Since Nick left Walford, he ended up back in prison again, where he received a letter from Sandy, learning that she had give birth to their daughter Dotty, who he didnt know existed, quite sometime before, he went back inside.
A while later, Nick was released from prison again, He then reunited Sandy, and was finally introduced to his daughter Dotty,
Nick and Sandy, rekindled, their relationship and got together, with him moveing in with her, and his daughter Dotty too, since that time, their relationship ended so badly, with Nick being sent back to prison once again, when he received cancer back in 2006, and fully recovered.
Upon Nick's early release from prison in April 2008, he took custody of Dotty, having told her that Sandy had died in a car crash. On the 16 February 2010, Dotty's mum arrives, showing she is not dead.
Dotty arrives in Walford Boxing Day 2008 with her father Nick, to see his estranged mother Dot Branning. Nick introduces Dot to Dotty and they quickly bond. He lies to Dot that he had promised to send money to Sandy on the condition that she named their daughter Dorothy after her grandmother, so that Dot will trust him and bond with his daughter; Dot does not know Dotty's real name. After spending the night, Dotty begs Dot to let them stay longer. Dot lets them stay for the rest of the week. Dot soon discovers that Nick hasn't changed; he doesn't have a job and he and Dotty have been living rough. Nick says he will either put Dotty into care, or sell her to Dot for the money that Bradley Branning had given her. After serious consideration, she buys Dotty, to get her away from Nick.
Dotty learns that Dot has made a will, leaving all of her money to Dotty when she dies. She tells Nick, and they form a plan to kill Dot in order to inherit the money. They trick her into thinking she is suffering from dementia. Eventually, Nick tells Dotty to give Dot an overdose of her medication by crushing up the tablets and putting them in her tea. However, Dotty has had a change of heart, and gives the pills to Nick in his beer. When Nick learns of Dotty's double-crossing, He drags her to the café and holds everyone inside hostage. Dotty manages to escape along with most of the others, but the café explodes, and in the commotion, Nick escapes. Later, Dot suspects her granddaughter may be just as evil as her father, So she plants some tablets on the kitchen table whilst Dotty has her back turned. Dot leaves the room, and then spies Dotty ignoring the tablets and pinching a chocolate biscuit instead. While practising for the nativity, Dotty causes trouble by being naughty, But vows to be good when 'Father Christmas' takes a visit to the community centre.
Dotty holds a birthday party for Dot, inviting Tiffany Dean and Liam Butcher, but they do not want to go. Dot tells Dotty that a lot of people cancelled. When Dotty looks out of the window, she waves at Tiffany, who pokes out her tongue. The next day, Tiffany tells Dotty she is not invited to her birthday party. Dotty tells Dot that Tiffany is not having a party and asks if they can invite her round. When they ask Tiffany's mother Bianca Jackson, Carol invites them to Tiffany's party. The next day, Tiffany and Dotty lie so they do not have to go to school. Dotty takes Tiffany's bridesmaid's dress and MP3 player and runs away with them, throwing the MP3 player into a bin in the Square. Tiffany tries to get it and then Dotty pushes her in. When Max Branning sees her, saying she should be in school, she runs away. When Bianca realises Tiffany's dress is missing, Jack says he saw Dotty with something by the bins. Tiffany will not say how she got in the bins, so Carol goes to see Dot, who says it is not like Dotty, who is a kind and gentle girl. Dotty tells Dot she knows nothing about the dress but Dot then finds it in Dotty's school bag. Dot returns the dress to Bianca without Dotty's knowledge. The next day, Dotty is left alone with Dot's husband Jim Branning who is recovering from a stroke. She pours water on him to make it seem he has wet himself, but Dot catches her. Dotty says she hates them both and wishes that Nick had killed her. Dot then very hardly smacks Dotty's bottom, making her squeal just as Jim's granddaughter Sonia Fowler, who is visiting, walks in. Dot apologises, but Dotty manipulates her into letting her stay off school. After Dotty calls the police, Dot is arrested for assault and Sonia tells Dotty off for making it seem like she was an abused child. However, Dot is released without charge but is told to expect a visit from Child Care. When Dot senior returns home, Dotty apologises.
Dot receives a visit from Dotty's mother Sandy, who Dot assumes is from Social Services, but she is looking for her daughter Kirsty. Dot says she knows nobody of that name but realises it is Dotty when she sees a photo. Dot hides Sandy's visit from Dotty but later talks to Sandy about Dotty and her past. When she goes home, she asks Dotty about friends and family she used to have, but Dotty says Dot is the only family she needs. However, Dotty soon admits that she misses her mother, and Dot reveals that she is alive and Nick had lied to her. Dotty says she wants to see her mother, so Dot calls her. When her mother Sandy arrives, Dotty is delighted and Dot tells Dotty she should go with her mother. They say an emotional goodbye, and Dot says she can visit at any time.
In October 2019, Dot returns to Walford after visiting family, and brings Dotty back with her, as Dotty was bored with her life in Wales. She returns and reveals she wants to study in London, and attends the leaving party of Bex Fowler, and begins to flirt with Tiffany's new boyfriend, Keegan Baker, Dotty later gives Bex the address of a drug dealer, who supplies some poisoneess drugs to her.
In January 2020, Dotty and Leo King begain having a brif fing but dosent last, with Leo calling Dotty "Whit", and she ends it with him for good.
Just after Dot Branning leaves Walford for good, and moves away to Ireland, to live with her grandson Charlie Cotton Jr, and great grandson Matthew Mitchell-Cotton, Dotty discovers the real truth to how her late father Nick Cotton really died, back in February 2015, and believed at first, that he died due natural causes, but it came out from Bex's drunken out burst, in the Queen Vic, when she revealed to Dotty, that her grandma Dot was responsible for father Nick's death, with Dotty asking questions and wanting more answers, and treating to go to Ireland to confront her grandma Dot, but Sonia Fowler begs Dotty to stay, and tell her the the full story to how Nick died, and reaveald, that Dot didnt kill him, he asked for her help, to supply him with heroin from his drug dealer, but Dot refused to let Nick go though with it, but soured it for him anyway, which Nick died from the heroin overdose, with Dot being there with him, and letting him die in her arms, with Sonia saying that her stepgrandma Dot, did it out of love.
In February 2020, While at the Queen Vic composition boat trip party, there is a massive accident, the boat ends up crashing, and Bex becomes very unconscious, then later taken into hospital, while Dotty ends up looking on, her's friend and colleague Dennis Rickman tragically dies, during the boat accident, she ends up discovering a voice message which revealed Ian Beale locked him up in a room, on the boat, in the lead up to the crash, Dotty begins to blackmail Ian, begging him for The Arches, otherwise she will end up exposing him, for what he did to Dennis.