GAH, this is UTTERLY BEAUTIFUL AND ADORABLE!!!
I'm also a huge fan of familial relationships, except my obsession is with surrogate father/son bonds, in particular, so yeah - Severitus material is AWESOME!
And your rendition of this theme is especially awe-inspiring!
P.S. If you're looking for an especially well-written fic that deals with a slow-mounting, but credible father/son undertone between Snape and Harry, I recommend "Emerald Eyes" by JadeSullivan from ff.net. Her sequel is a WIP and it contains CP (corporal punishment), but it's been my all-time favorite. This is why I love fandom power, hehe.
Thank you again for posting/sharing this gem!