Mob boss Sonny Corinthos learned that he had a cousin named Gladys Corbin when his father Mike Corbin first mentioned her during one of Mike's lucid moments. Mike had been struggling with Alzheimer's disease, and he had mistaken a teenage boy that Sonny had taken in as Gladys' son, Brando. Gladys had raised her son in Bensonhurst, New York, but she had moved to Bridgeport, Connecticut in later years. Sonny decided that he could use Gladys' help because Sonny needed help keeping Dev Cerci in the country.

Dev had helped when Sonny had gone to Turkey to rescue his son. Dante Falconeri had been working undercover for an international arms dealer, and Dev had aided Sonny accessing the compound. Later, Dev was taken to the World Security Bureau's headquarters, but he balked at letting them set him up with a new life. Instead, Dev escaped their custody then made his way to Port Charles to seek sanctuary with Sonny. Sonny opened his home to the teen, but Dev was in the country illegally. Fearing that Dev would be deported, Sonny decided to create a false identity for Dev as Sonny's teenage cousin, Devin Corbin.

On July 3, 2019, Sonny met Gladys at a café in Bridgeport. Gladys instructed Sonny to get to the chase because she knew that he wanted something since she hadn't heard from Mike in ages. Sonny asked about Gladys' son, Brando, so she informed him that her son had been killed while stationed in Iraq in 2003. According to Gladys, that had also been the last time that she'd seen her cousin, Mike.

Sonny explained that he needed Gladys' help with a project, but she cut him off because she knew that Sonny was a powerful mob boss and she wanted nothing to do with his illegal activities. Sonny mentioned her grandson, but Gladys clarified that she didn't have any grandchildren. Sonny smiled as he slid a thick envelope across the table to her. He assured her that the envelope was the first of many that would arrive every six months. In exchange for the generous payments, he expected her to tell the government officials who would stop by to talk to her that her son Brando had married in Iraq and had returned home with his wife, but the poor soul had died in childbirth.

Gladys realized that Sonny wanted her to help him cover-up for a child in the United States illegally. Annoyed, she informed Sonny that the envelope wasn't thick enough then slid it back to him. Undaunted, Sonny advised Gladys to look again, but Gladys was afraid that she would be arrested for helping Sonny. Sonny retrieved more money from his wallet then added it to the envelope with a promise that she would get the same amount every six months.

Sonny pointed out that if Gladys had done her homework, then she knew what would happen to anyone who double-crossed him. Reluctantly, Gladys accepted Sonny's terms. Pleased, Sonny told her that she would receive a packet of information about her grandson that he expected her to memorize.

Sonny was satisfied with the arrangement until he discovered that Gladys had checked Mike out of Turning Woods and taken him to Metro Court Restaurant. Gladys explained that Mike had insisted, and that her cousin had regaled her with stories about the past. Mike appeared oblivious to the tension between Gladys and Sonny as he told Gladys that he wanted a handball rematch with her boyfriend "Frankie" the next time that they got together. Gladys tactfully explained that "Frankie" was no longer around, but she didn't elaborate.

Gladys continued to visit Mike, and she would run into Sonny and his wife Carly on several occasions. Both Sonny and Carly questioned Gladys' intentions, but she assured both that she genuinely cared about Mike. Gladys also made a point of seeking out Dev because she wanted to keep up the pretense of him being her grandson. The encounters were awkward and brief because Dev was uncomfortable around Gladys.

As Christmas approached, Sonny had an encounter with Gladys at Turning Woods. She opened up to him about her best friend who had recently died of Alzheimer's disease. Sonny felt bad for Gladys when she confessed that it was difficult being alone for the holidays, so he invited her to spend Christmas with him and his family. However, Gladys soon overstayed her welcome, prompting Sonny to buy her a new car. He explained that she would have reliable transportation to get her from Bridgeport to Port Charles whenever she wanted to visit Mike. Gladys asked if she could stay until Sonny and Carly's daughter was christened because Donna had a special place in Gladys' heart.