Jack Marone is the biological child of Nick Marone and Brooke Logan. Nick had just married Brooke's long-time nemesis, Taylor Hayes, and together, Nick and Taylor decided they wanted a baby. But Taylor had fertility issues, so she and Nick decided on in vitro fertilization. Taylor carried her child to term and gave birth to a boy, whom she named Jack, after her father, Jack Hamilton. But when Taylor wanted to locate her egg donor because the Jack needed a bone marrow transplant, Bridget Forrester (Taylor's doctor and Brooke's daughter) was forced to admit there had been a mix-up in the lab. Taylor, Nick's current wife, and Brooke, Nick's ex-wife, both shared a last name of Marone, which was attributed to the confusion: Taylor had given birth to a baby conceived with Brooke's egg. Jack recovered after receiving bone marrow from Brooke.
Taylor was beside herself and had trouble coping when she couldn't bond with baby Jack. Taylor's drinking problem resurfaced, so Nick filed for custody with assistance from Brooke, who couldn't stop thinking about her biological son. Ultimately, Nick and Taylor, who had divorced, received joint custody of Jack, but when Jack still didn't respond to Taylor's attempts at mothering, Taylor asked Brooke to raise Jack instead.Jack briefly became a source of obsession for Brooke's sister, Katie Logan, who had just miscarried a baby of her own. Owing to Nick's multiple romances, Jack has had Katie, Bridget, and Agnes Jones as mother figures in addition to Taylor and Brooke. Nick developed a spot on his lung but still wasn't convinced to give up smoking cigars until he watched cigar smoke wafting into Jack's face. For the most part, Jack was occasionally referenced and seldom seen in his childhood.