Debra Stewart is the younger sister of Alf Stewart and his other siblings Colleen Smart, Morag Bellingham, Celia Stewart and Barbara Fisher. She was seen in a flashback to her brother Alf's 5th birthday in 1950.
Birthday: Unknown (As early as 1947 or late as 1960, the H&A scripts are ambiguous)
Full Name: Debra Stewart
Debra has been mentioned a few times but has never appeared in the show. The birth order of the Stewart siblings did originally suggest she was the youngest but Alf had a flashback to his 5th birthday in 1950 and Debra was there, making her about the same age as Barbara.