Lisa Jackson is the mother of Dwayne and Zayne Jackson. Her alcoholism meant that they spent 8 years in the care system before Joe Casey and Mike Rutherford fostered them. After getting sober, Lisa takes interest in getting her children back, sending them a letter which Joe refuses to give them until she shows up at Waterloo Road High School asking for him.
Dwayne is keen to live with his mum again, causing a rift between him and Joe, who still suspects that Lisa can't be trusted. Ultimately, Dwayne and Zayne are allowed to stay with Lisa occasionally, whilst still staying with Joe and Mike most of the time. This gets off to a rocky start when Lisa brings Dwayne and Zayne into school late, not having even fed them breakfast.
Lisa hasn't been seen since the end of Series 12, but it is presumed that Dwayne and Zayne continue to see her off-screen.