As someone who isn't all that interested in having children myself, I can't really see Katsa's choice to not have children as selfish. Rather, I think her choice is the responsible one - she knows she wants to be free to run around and do what she wants, which includes putting herself in danger in order to help other people, and if she had a child it would be impossible to fulfill her goals.
I met Kristin Cashore at a book signing in November and actually asked her why she had written two characters that were so adamantly against children (especially since we rarely see characters that have an opinion on that in YA). She brought up an excellent point: although both characters have the same desire (no kids) they manifest in entirely different ways: Katsa actually draws strength from her choice, while for Fire it's a great tragedy, and while the choice doesn't play out in the narrative as important, those are important character-shaping moments.
As someone who wants to have kids I failed to take into account those who would rather not. Even if that reason had more to do with personal preference. I was unfair to Kristin Cashore and her character, Katsa, and I believed that this quote from someone more knowledgeable about that subject made an excellent point about Katsa and Fire.
There are people out there who simply don't want marriage or children for no other reason then they just don't want children. I'm glad that someone pointed this out, and called me on it. I'm even more glad that this person wrote about what Kristin Cashore had to say about her books and her characters.
So thank you Angela for pointing this out. It was really nice to hear from you, and I'll be reading your blog in the future.