Professor Callum and his wife are the parents of The Ds, Dick and Dorothea Callum. Professor Callum is an academic archaeologist, and is often correcting examimation papers. Neither Prof Callum or his wife have brothers, as Dick and Dorothea have no uncles of their own (WH23). But the Ds have aunts, as Dot thought of other aunts they knew, most friendly, kindly creatures (unlike the dreaded Great Aunt; PM3)).
Mrs Callum, accompanies Prof Callum him on conferences and expeditions. Mrs Barrable used to be her school-mistress, and Mrs Dixon used to be her nurse. It should be noted, therefore, that during Mrs Callum's childhood, Mrs Callum, Mrs Barrable and Mrs Dixon were all living in the same area; this could indicate that Mrs Callum is originally from the Lake region, like Mrs Dixon.
The Callum parents probably live in London: London last night, and now Beckfoot (PM2).
- Winter Holiday: they have gone to Egypt to dig up remains (WH3). Mrs Dixon had been their mother’s nurse when she was a little girl (WH1).
- Coot Club: Dorothea says Our father’s an archaeologist and as their parents were going to a conference of archaeologists upon the Roman Wall the Ds are off to stay with Mrs Barrable who long ago, had been Mrs Callum’s school-mistress (CC1). Later, when the Teasel arrives in Potter Heigham, Dot sends a picture post card to her mother, saying: This is our first port of call ... like Malta was when you and father went to Egypt (CC13).
- Pigeon Post: the D's father is correcting examination papers (PP1)
- The Big Six: the Ds first appear in (BS9), but there is no mention of their parents.
- The Picts and the Martyrs: the Professor is busy for a fortnight in London correcting examination papers (PP1). Later when the Ds are living in The Dog's Home they get letters from Mother; saying they would presently be teaching (them) how to sail (PM7), and later Mind! No getting drowned. We want to learn to sail and hinting at a boating holiday on the Broads ..... (as Father is) looking at a catalogue of boats for hire on the Broads (PM14).
- Great Northern?: When Father found a Pharaoh's tomb, he spent two winters working at nothing else (Dorothea, GN10). Once when he couldn't be sure whether a tomb was third or fourth dynasty, or something like that, he couldn't think of anything else at all until he'd found out (GN7).