This is my headcanon appearances for Pinkie and Blueblood along with headcanons about him and how the two of them got together.
 
His full name is Vladimir Atlas Blueblood The Second, Pinkie however calls him Vlad, Vlady, or Blue. (Credit for the Headcanon name Vladimir Blueblood goes to Lopoddity)
 
He’s a direct descendant of Princess Platinum, hence why he’s gotten the title of “Prince” and is Celestia’s adopted nephew. His mother was named Opal Aurorus and his father is Vladimir Blueblood The First. His mother was a very sweet and kind mare who died when he was a colt from Equine Encephalomyelitis (“Sleeping Sickness”), the last few months before she passed were incredibly difficult on Blueblood and his father. Blueblood reached out to his father hoping to comfort him while his father became more and more distant. After his mother finally passed his father became colder to him and spent most of his time in the company of different mares almost every night. Blueblood spent most of his life after his mother’s passing being told that he was better than everypony because of his bloodline and that he could do as he pleased, he followed the example his father set and became almost a carbon copy of him.
 
That soon changed after an incident that caused Celestia to decide that he wouldn’t live in Canterlot until he learned how to feel empathy for those around him, so he was sent to Ponyville. He had trouble adjusting to “common life” and tried to lord over and use the ponies around him but that only led him to being cast out alone and homeless in the rain. Pinkie Pie took pity on him and brought him to Sugar Cube Corner and the two were almost inseparable after that, and she became a shining light in his eyes. He learned from Pinkie how to care for the feelings of those around him and how much a real smile could mean to someone, as well as work ethic. He learned how to do things for himself and eventually began working to help the ponies in Ponyville with all sorts of odd jobs, learning more along the way. He didn’t realize he really loved Pinkie until after he’d been allowed to return to Canterlot and saw almost everypony’s true nature. He left back to Ponyville and proclaimed his love for Pinkie, praying she’d say yes to marry him. Pinkie had felt heartbroken when he left but didn’t think he’d actually come back and was more than overjoyed when he did, she said yes to his proposal and they were married soon after. His father was incredibly displeased and the two haven’t had a good relationship since.  
He is extremely devoted to his wife, Pinkie Pie, and the family they’ve built together, after realizing how much different he is he tries his best to not fall into old habits or fall in with the wrong crowd again. He sees a lot of his past self in his daughter Aurore Beau Monde and has tried to keep her from having to learn the hard way like he did, but she’s stubborn and refuses to listen.
 
He loves to cuddle with his small, chubby, bubbly pink wife and dotes over her and their children. He would’ve very nearly spoilt them both rotten if Pinkie didn’t step in to remind him at times that they can’t have exactly what they want all the time.
 
He now runs and goes to charity auctions, he knows that with his status if he gives money for something others will as well and it’s one of the many ways he tries to help those in need.  
His special talent is cartography and map making, he also teaches culture classes at Celestia’s School For Gifted Unicorns in his spare time.