There are so many characters and so many brilliant pairings, this verse's ship chart is overlapping in so many areas. I think I'm going for a "love is shared, and it's very common for a pony to have many partners throughout their life, with polyamory being the norm". Each relationship offers such a different but equally deep connection, and love is sorta what keeps the MLP world running. It's a literal magic. So some ponies may have none, or only one partner through their life, while others may have many at once, all with their own history and timeline.
Story is long, the basic premise is
BB: Hey shawty SA: Get off your mfing high horse and we'll talk, you posh jerk
———
Here's the general timeline for their whole deal!
The first time they meet: Shining Armor and Blueblood are both invited to a meet-and-greet social, as the Captain of the Royal Guard and the Duke, respectively.
They acknowledge each other at the snack table, then again on the social floor, when Shining Armor strikes up a casual conversation. He cracks a few jokes, and Blueblood starts to finds the Captain charming. It's a genuine connection, just something small. A royal with a raised eyebrow and an amused smile, alongside a strong stallion with a loud laugh and a great sense of humour.
The event moves on and they part ways.
——-
Cut to a few months later.
The Grand Galloping Gala is coming up, and everypony is ready to go. Blueblood, a pony who has really become a nasty piece of work in the last few days, will be attending. Or, at least, someone who looks like Blueblood. It turns out the Duke had been replaced with a changeling.
The real Blueblood will appear in a couple days with memory loss.
The changeling's intent was to test out the power that Blueblood's title gives it, and to scope out Canterlot royalty and high-end security. It was a pretty huge jerk to everyone in that time, and when the real Blueblood appeared after a week with no idea what happened, there were a LOT of people mad at him.
The social stigma of that sent Blueblood into a slight spiral, during which he grows a bit irritable, conceited, and a frequent partaker of alcohol. After all, if the tabloids were going to call him a drunkard due to his "unruly behaviour" and the memory loss that stole his recollection of it, he might as well give in.
——-
Shining Armor attends a social gathering a month later. He subconsciously keeps an eye out for the hard-to-please stallion he met at a previous party. Eventually he spots Blueblood at the drink table with a number of high class ponies surrounding him.
Blueblood's tongue is loosened from sweet wines, and he joins the snobbish crowd in their rude comments and glances at the other guests. Then he notices Shining Armor staring at him a few yards away, and Blueblood's face splits into a grin. He calls over the Captain and introduces him to the group, pulling him about by his foreleg like some sort of show-and-tell display.
The group makes their comments and performs their faux show of interest towards Shining Armor. During this, Blueblood isn't making a good show of himself. He's pushy and loud, a sort of overconfidence that whispers of insecurity.
Shining Armor puts up with the rudeness for a few minutes before politely bowing out of the conversation and moving aside. Blueblood follows his lead, still talking about whatever he had been prattling about with the snobs.
Shining Armor makes a sideways comment about manners, which Blueblood doesn't catch. The Duke just offers to get Shining a drink.
Shining recoils, making a face. He declines the offer. Though he had been interested to see Blueblood again, the other stallion's manners had changed.
Blueblood dismisses Shining's answer and insists.
Shining Armor jerks away from him, his brow furrowed with irritation. Blueblood's behaviour grated against him, rightfully so, and he wasn't interested in talking with the Duke if he had changed that much since their last meeting. He says so, telling Blueblood that until he got over whatever baggage was making him act like a tool, he wasn't interested.
Blueblood is shocked and insulted, and self-preservation rears its head to twist those emotions into anger. He doesn't have time to do more than splutter before Shining Armor trots off to enjoy the party from a different room.
(spoiler alert: Blueblood will eventually heal and pursue Shining properly)