Rainbowblood is some good shit
 
In my nextgen, Prince Blueblood never really knew what love was until he met Rainbow Dash, the reason he treated Rarity and other mares the way he did is because he had no romantic interest in them and he suffers from NPD. at first he did not notice Rainbow Dash, dismissing her as another boring underling, but as he saw her around Canterlot and observed her, he slowly began to fall for the pegasus, he’d always been around snooty, high class mares, sure they were beautiful, but to him Rainbow Dash was more than beautiful, she was exciting and… different. For the first time he was attracted not only to who she was on the outside, but the inside as well. For months he persisted, trying to get her to notice him, for a long time Rainbow showed no interest due to what he did to Rarity, but eventually she gave in and decided to give the strange prince a chance. On the date, they learned that despite being so different they also had a lot in common, for example they’re both competitive and they’re both adrenaline junkies who love going on adventures. Soon they developed a serious relationship, and eventually got married.  
Blue and Rainbow often tease each other, Rainbow makes fun of him for being a vain, spoiled prude who hates getting dirty, and Blue makes fun of her for being a stubborn, boastful meathead. Obviously, it’s all in good fun and never meant to actually hurt each other, after all, they’re madly in love.  
Rarity never forgave Blue for what he did, so while Rarity and Rainbow Dash are still on great terms, Rarity is not a fan of Blueblood. Also, although Rarity would never admit it, she’s slightly aggrivated that Rainbow became a princess even though it was HER dream.