Sheila Jackson (previously Sheila Gallagher) is the thrice married second wife of Frank Gallagher. She is the mother of Karen, who she had with second husband Eddie Jackson, and of twins Nigel and Delia Gallagher, whom she had with Frank in 2005.
Sheila is introduced to the series as a severe agoraphobic, locked in an unhappy marriage to Eddie Jackson, who holds radical Christian beliefs and provides Sheila with a non-existent sex life. Upon catching their daughter Karen giving oral sex to Ian Gallagher in their kitchen, Eddie flies off the handle and chases Ian and Lip down. He then packs his bags and leaves the house, never to return.
Eddie meets Frank Gallagher in the pub and, knowing that he's the father of Ian, he headbutts Frank and knocks him out. Later on, he buys Frank a pint and sits down with him to vent his frustration about the sorry state of his marriage and family life. When he talks about Sheila's many disability checks and lust for sex, Frank immediately ditches him and arrives at Sheila's house, apparently to apologize for his sons' behaviour.
Sheila is instantly enamoured with him and offers him a bath with hot water, a luxury he doesn't have at home. The two then go on to have sex, although Sheila insists on tying Frank up and giving him anal sex with her dildo collection. She goes on to fall deeply in love with Frank and falls pregnant, eventually giving birth to twins Nigel and Delia at Christmas 2004.
Sheila suffers from agoraphobia and is a fan of daytime television, especially Countdown, finding it unbelievable that someone doesn't know who Carol Vorderman or Richard Whiteley are. She named her twins after famous chefs, Delia Smith and Nigel Slater. Sheila left with the twins to go on a cruise after discovering Frank had not divorced his former wife Monica, who had suddenly reappeared with her lesbian girlfriend, and that Sheila's marriage to Frank was not legally valid.