They were first introduced in February 1990, when brothers Phil (Steve McFadden) and Grant Mitchell (Ross Kemp) bought the local garage, the Arches.
Their sister Sam (Danniella Westbrook/Kim Medcalf) was introduced later in 1990, and their mother Peggy (Jo Warne) shortly after in 1991, before being reintroduced as a regular character in 1994, with the role recast to Barbara Windsor.
Phil has been the longest running Mitchell on the show, and the family has expanded significantly in the years since, remaining a large presence on the square.
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In 2016, Windsor, Kemp, and Westbrook briefly reprised their roles as part of a major story line that follows Phil's ongoing battle with alcoholism and ends with Peggy's suicide due to terminal cancer.
Throughout their time on the show, the Mitchells make several references to their late patriarch Eric (George Russo), who first appeared in 2022 during a flashback episode to 1979 and served as a recurring impact for most of the family members, especially Phil and Peggy.
As of 2025, a total of thirteen Mitchell blood relatives appear on the programme: Phil; his sons Raymond Dawkins and Albie Watts; Ben's daughter Lexi Pearce (Isabella Brown); Sam's son Ricky (Frankie Day) and his daughter Charli Slater; Roxy's daughter Amy (Ellie Dadd); Phil’s cousins Billy (Perry Fenwick) and Teddy (Roland Manookian); Billy's children Janet (Grace) and Will (Freddie Phillips); and Teddy's children Harry (Elijah Holloway) and Barney (Lewis Bridgeman).
There are others that have married into the family such as Phil's ex-wives Kat Slater (Jessie Wallace), Sharon Watts (Letitia Dean) and Kathy Beale (Gillian Taylforth); Billy's ex-wife Honey Mitchell (Emma Barton); Teddy's ex-wife Nicola Mitchell (Laura Doddington); and Ben's husband Callum Highway (Tony Clay).
In 1993, Phil marries Romanian immigrant Nadia Borovac (Anna Barkan) to let her stay in the country, but starts a relationship with Kathy Beale (Gillian Taylforth) at the same time.
The Mitchell empire falls when Den blackmails their old friend of the family, Marcus Christie (Stephen Churchett), into scamming them of all their assets.
Phil gets engaged to Stella Crawford (Sophie Thompson), unaware that she was physically and mentally abusing Ben behind his back, which gets revealed on their wedding day.
The wedding introduces Phil's cousins, Ronnie (Samantha Womack) and Roxy Mitchell (Rita Simons), as wild and fun-loving sisters from Ibiza, who buy the local club, R&R.
Suzy Branning (Maggie O'Neill), Phil's latest girlfriend, reveals on Christmas Day 2008 that Roxy's husband, Sean Slater (Robert Kazinsky), is not Amy's father, resulting in their divorce.
Danielle Jones (Lauren Crace) arrives in the square in 2008, and is soon revealed to be the daughter Ronnie gave up for adoption many years earlier.
However, Ronnie discovers the locket in her wine glass, and heads off to reunite with her daughter, who is killed by Janine Butcher's (Charlie Brooks) speeding car.
Determined to help her son break his addiction, she locks Phil in the Queen Vic, but he escapes and sets the pub on fire.
However, days after he was born he died of sudden infant death syndrome, and she swaps her dead child with Kat and Alfie's newborn son.
Ben (now Joshua Pascoe) is released from prison in September, and began to stalk Phil when the latter refuses to accept that he is gay, sending him threatening notes for several months.
Billy's granddaughter Lola Pearce (Danielle Harold) is introduced as a new teenage troublemaker, and is impregnated by Ben, her distant relative, when they test his sexuality.
Jill Marsden (Sophie Stanton) returns to arrest him and accuses him of murdering Stella Crawford after her abuse is exposed.
Ben panics about his father's return, and kills Shirley's best friend Heather Trott (Cheryl Fergison) while arguing with her.
Their marriage is rocky; Kathy is revealed to have faked her death and returns, while her husband Gavin Sullivan (Paul Nicholas) makes Phil become addicted to alcohol again.
Billy reunites with Honey when she returns from Canada, and Roxy leaves for a while to get over her attempted rape by Dean Wicks (Matt Di Angelo).
Ronnie briefly marries Charlie Cotton (Declan Bennett), the father of her newborn son Matthew Mitchell-Cotton.
Phil then tracks down his daughter Louise (now Tilly Keeper) to right wrongs, and learns that Peggy is also dying from a relapse of breast cancer.
In 2016, Peggy commits suicide rather than face a slow death from cancer; Grant discovers he has a son with Michelle Fowler (Jenna Russell), named Marcus (Ned Porteous); and Phil remains sober for long enough to receive a liver transplant.