Harry rescues dudley's son
I can't seem to find this but Dudley is married to someone in the Snape line (she is a Squib), they have a child who turns out to be magical I am pretty sure the child is called Alex. Harry removes both the child and the wife of Dudley who wasn't treated well. Harry does something to a book and finds out she is related to Severus. Severus was working on a male pregnancy potion and Harry aids in some way there was somethign about a charm preventing cancer causing problems with his potion. Severus resigns from Hogwarts any suggestions?