Based on having a bout of really great sex, Lorelai and Christopher decide they should be a family now (boy, that must’ve been some sex they had!). Lorelai says, “This thing with Sherry is so recent” – mm, so recent it’s not actually over, Lorelai! But when you can downgrade someone’s relationship into a “thing”, I guess it’s easier to justify.
They say it’s the best thing for Rory, but I don’t think either of them are really thinking about Rory too much at all. Neither of them discuss how they will break the news to Rory, and Lorelai doesn’t stress to Christopher that he can’t let Rory down any more, or give her a few minutes of phone time once a week and call it fatherhood.
While Christopher has always been trying to get Lorelai for himself (even getting a girlfriend was apparently part of his plan to win Lorelai back), Lorelai seems to be going along with this because she’s unhappy without Luke’s friendship, and because watching her best friend prepare for marriage to the man of her choice has left her feeling even lonelier. It’s not a great basis for a relationship, let alone a family.