Jack Croston was the brother-in-law of Elsie Seddon.

Jack and his wife Bertha were contemptuous towards Elsie's abusive husband Eddie and shed few tears when he died in a road accident in January 1989. The couple were among the few mourners at Eddie's funeral, attending to support Elsie, and went along to a luncheon at 13 Coronation Street organised by Sally Webster afterwards. Reflecting on the service, at which the vicar had praised Eddie's character, Bertha remarked that the vicar couldn't have known Eddie to say those things about him. Jack then interjected, calling Eddie a bad 'un, but with respect to Elsie in her time of grief. Under no illusions about the kind of man Eddie was, Elsie admitted that they were right but that she missed him anyway.

Jack didn't drink tea.