The Blacketts really are absent parents in a way the others aren't - I'd forgotten that Mrs. Blackett was a widow because they feature so little! And that makes Nancy's Amazonian-ness even more curious, because she certainly didn't get it from her mother, or not in any obvious way. I seem to recall the book explicitly commenting that Nancy in some ways gets that from her GA, which is interesting, because you've got this great contrast between the GA, who is a strong independent woman and an absolute terror to everyone around her, and Nancy, who is also strong and independent and likes to have her way, but is much more willing to compromise. It's another good example of how Ransome has different models of female behaviour and leadership. (And then there's Missee Lee, who is also a female leader, but has much more of a sense of duty than anyone else we see except perhaps John.)

Reading Wiki, I am reminded that Roger, Susan, and Titty were named after the real-life Roger Altounyan, a Syrian scientist, and his sisters, which also makes me think that the S&A series is a good one for positive mentions of science; between Dick's astronomy and the map-making and the bird-hunting and the copper-mining, as well as the North Pole expedition, there's a real focus on practical exploration of the natural world which I particularly like. Learning is presented as this positive and *useful* thing, with real-world applications. I'd like to see more of that in kids' books, for sure.