What I think I love most about this one is that it shows how interconnected they are. Dean has this relationship with Sam's kids that is different from Sam's relationship with them but no less essential. And the same with Sam and Charlie. Moms notwithstanding, it's like all the girls needed both brothers in order to have a complete family. The boys always filled in each other's missing pieces, and now they do it for each other's kids as well, and that is just so lovely and perfect and why this AU has been/is/will be so much more than just fiction.