Jacob Gallagher is the adoptive son of Alicia Harding and the biological son of Leyla Harding. He was conceived after Leyla had an affair with her brother-in-law Justin Gallagher. Leyla's sister and Justin's ex wife Alicia brought up Jacob as her own child. Leyla gave Jacob to Alicia was he was born due to Alicia being infertile.
Alicia and Justin split up in 2010, and Alicia and Jacob moved to the village. Due to Alicia's job, Jacob spent much of his time with Leyla and her boyfriend David Metcalfe. Leyla nearly told Jacob she was his biological mother, and the strain of silence led her to leave town after about a year. With Justin now starting a new family, and David and Alicia slowly falling in love, Jacob began to see David as a father. In later years he would begin calling David "Dad."
Jacob did not know about his true parentage until late 2013. He became very upset when he found out that Alicia wasn't his biological mother, and ran away to his best friend Noah's house, where he stayed for a night. When Leyla returned to the village, Jacob was angry and confused, but he eventually accepted her as part of his life, while still seeing Alicia as his mother.
2015 was a year of violent upheaval for Jacob, as he struggled to cope with Alicia's sexual assault by Lachlan White. In a fit of rage, Jacob vandalised Home Farm. When Alicia realised she could no longer live in the village, she and Jacob moved to Portugal. Mother and son were heartbroken when David chose to stay in the village, and Jacob chose not to contact him for some time.
In 2016, Jacob returned to the village, unhappy with his new life in Portugal. Alicia contacted David and Leyla frantic as Jacob had left without telling her; they convinced Alicia to let him stay in the village. Jacob had a crush on Gabby Thomas, but when she told him that she and Lachlan had broken into Eric Pollard's house and stolen a piece of jewelry belonging to his late wife Val Pollard, a disgusted Jacob told David. An angry Gabby fell out with him, but they eventually made up.
David learned he had testicular cancer, and, unable to face telling Jacob, instead sent him back to Portugal for a holiday. Jacob soon returned early, surprising David. David continued to lie to Jacob, but soon had to tell him the truth. Jacob was hurt by the lies, and stole Eric's credit card for a plane ticket back to Portugal, but Tracy Shankley convinced him to stay in the village to help David.
- Jacob is allergic to nuts.