From the Walkers' perspective, most definitely, I think, though I was struck by how much more present Mrs Blackett is in this book - nursing/trying to contain Nancy, even coming to the North Pole than she normally is. And Captain Flint is around a lot. But the Calums are in the same position as the Walkers, in terms of their staying at a farm without their parents who've gone abroad, yes (but the Calums' mother's childhood and Mrs B and Cpt Flint's childhood are discussed - emphasising the similarities between them and their children). It's hard to tell because we see the beginnings of the friendship through Dorothea's perception, not the others.