So I can't remember the title or where I read this. There's some kind of contract that says Harry has to marry Ginny. He can't get out of the contract but he can renegotiate it. So he rewrites a lot of it and somehow keeps it from the Weasley's and Dumbledore. It makes it so they can't get their hands on his money and he won't have to actually have sex with Ginny. The night before the wedding he goes to Snape and asks the man to sleep with him. After the wedding Harry gives Ginny a potion so she can get pregnant if she wishes, one of the terms of the marriage is she has to give the Potter and Black lines an heir. Through the whole marriage she's a brat and no one in high society approves of her, and I think while her mother supported the contract the rest of the family didn't. Harry is actually friends with the Malfoy's, I think they helped him with negotiating the contract. Their marriage ends because after she has a daughter Ginny thinks she's produced an heir and starts to have an affair, but a son was required to fulfill the Black requirements. Harry eventually is able to start seeing Snape at the end.