The Second Son is a significant chapter name, bringing to mind Cain (the first son to be born, but the second to die) and Franco himself, whose villainy came to overshadow that of his firstborn brother Joe. With this in mind, it nicely foreshadows Michael Begbie's reveal as a scumbag himself, like Cain and Franco before him.
For those who have followed Begbie since Trainspotting, we know he's always been violent and dangerous, but we could take comfort under the assumption that he never went as far as murder until the interim period between that novel and Porno. From this novel, the assumption proves false as, even if it was a Mercy Kill, Begbie broke the taboo of killing another human being as early as his teens. This colours our intepretation of him as we re-read the earlier novels.
