Can't wait to see what will unfold in the next few chapters. I really liked the description of the spell that Severus, Poppy and Minerva used to help Ginny. I'm curious to see if/when Harry finds out that he is Snape's biologically. Did the potion Lily use make Harry look like James or also introduce James' genetics so Harry would/could pass a blood test as a Potter? Severus' dreams make it seem like James knew about what Lily had done, did he?
Author's Response: No one is altogether sure how deep the changes from the potion are, it's very old. Basically, Harry is a Potter because James accepted Harry as his when he was born (this come from British Common Law inheritance law), the Occludus Potion causes the child to resemble the purported father, so no one asks sticky questions.
Since James Potter is dead, Snape can press his blood claim because he's closer in blood than Petunia. If James Potter were still alive, due to the Magically Binding Contract of accepting Harry as his heir, James would have the stronger claim.
It's not so much blood, as a complex line of magical kinship.