It's so, so weird that Sue tags along on literally every foreign trip that Billie and Greg go on: holidays, weddings of people Billie knows who are a generation younger than Sue, photo shoots, the lot. I don't know any other family where the dynamic is like this. It's like Billie and Greg don't have enough going on between just the two of them to sustain things. It speaks volumes that Greg doesn't seem bothered with Sue tagging along; on the contrary. But most men I know would run a mile if their mother-in-law came along on every trip they took.