Ron wants to be consumed, owned, possessed. He wants it all, and Hermione wants him to be hers just as badly. Perhaps even moreso.

The all-consuming feeling of being owned was addictive. When Hermione offers him another chance at the feeling, he struggles to do the right thing. *mind tags before reading

Harry's a good friend. But when he tells his best friend that he'd do anything for her, he doesn't expect to be offering to father a child with her to save her from the impending Marriage Law.