Rory Williams character study: I don’t know what he said to you to make you marry him
Brian was a late addition to Rory’s story, but in his very first scene, it’s clear he may be the root of Rory’s Amy-related insecurities (of which there are many.)
We know Brian’s fantastic, obviously, but look at this scene- without even realising it, Brian’s expressing disbelief that Rory could ever get a girl like that to marry him. And Amy, being Amy, plays at being Brian’s favourite. Perfect as ever!
I can imagine similar jokey comments heading Rory’s way whenever the three were together- Brian possibly so impressed by Amy he forgot his own son had achieved a lot in life too. (We know that Brian’s never seen Rory’s nursing skills in action.) We know Brian’s comment and any previous comments he may have made about the Amy-Rory marriage were made in jest, but it’s entirely possible they ate away at Rory. What he took from them was almost certainly, “Even my own father doesn’t think I’m worthy of someone as incredible as Amy.” Which is the sort of thing that would mutate over the years, make you insecure and jealous…but more on that later.