The O'Connors - a four-member Liverpudlian tribe - descend on the fictional Chester village in the summer and bring with them a hoard of heartache and family baggage.
Fletcher - who played the role of Jacqui Dixon in Brookside - has signed to play the part of Diane O'Connor, a step-mother of two who's desperate for a child of her own.
However, with her biological clock counting down by the day - and her second round of IVF apparently destined for failure - her need for a baby quickly spirals out of control.
Her drastic attempts to secure a child of her own, however, poses a threat to the family unit she's already part of.
Meanwhile, Diane's husband Rob - played by Gary Cargill - joins the ranks as deputy headmaster of Hollyoaks High.
With him, he brings his two children 15-year-old Sinead - portrayed by Over The Rainbow contender Stephanie Davies - and 12-year-old Finn (Connor Wilkinson).
Speaking of her role, Fletcher said: "I am delighted to be back filming at Lime Pictures where I started my career on Brookside - then Mersey TV. I worked with Paul on Brookside and I'm thrilled and honoured to be working with him again, especially as this is such an exciting time for Hollyoaks.
"I can't wait to see what else he has in store for the O'Connors and the show. And I'm really looking forward to working with Gary, Stephanie and Connor. We've already connected as a family and my real daughter was a huge fan of Over The Rainbow so she'll be delighted when I tell her that Stephanie is playing my daughter in Hollyoaks!"
Producer Paul Marquess commented: "We're very excited about the arrival of the O'Connors who burst onto screens in August with a very dramatic story-line. And I'm personally very excited to work with the fantastic Alex Fletcher again."
The O'Connors - who make their first appearance in August - are the latest in a string of signings by Marquess, who was tasked with the responsibility of turning around the soap's fortunes. He also masterminded the show's two other new families, The Sharpes and The Costellos.
Newcomers include former Footballers' Wives actress Phina Oruche (Gabby Sharpe) and ex-Bill star Kim Tiddy (Heidi Costello).