Duncan is born to Alf and Ailsa. After his aunt Celia (Fiona Spence) dresses him in the Stewart family's traditional christening gown, he suffers an allergic reaction to it and is hospitalised. Duncan recovers, but Ailsa experiences post-natal depression and nearly smothers him at one point. Ailsa soon begins to bond with him. As Duncan grows older, he befriends Christopher Fletcher (Shaun Wood) and has several surrogate siblings in the form of Blake (Les Hill) and Karen Dean (Belinda Jarrett), Simon Fitzgerald (Richard Norton), Sarah Thompson (Laura Vasquez), Curtis Reed (Shane Ammann) and Aaron Welles (Ritchie Gudgeon), teenagers whom his parents foster.