Claudis and Midnight knew each other prior to the events of Capricorn Reef. Midnight was called to help a ‘dying’ dragon in the dungeons of Canterlot. When got there what he found was a rare, thought to be extinct species of Dragon that was freezing cold and going into a hibernation stage. Angered and not having too many nice words for the ‘stupid rainbow princess bitch’ that called for him, he got to work on treating him.
He uses anything he can, blankets, heat lamps, heating appliances to make sure that Claudis gets warm. He also starts bringing him in meat, which they had been seemingly refusing to do. It took a long time, but Middy eventually gets Claudis healthy. He visits and checks on his progress until he gets word of an attack on Canterlot Castle. He finds Claudis gone the next day.
It was 2 years later that Midnight found him in Ponyville, visiting his daughter and newborn granddaughter. Taking a leap of faith, he makes the chance to reconnect with him.
It takes almost 6 months for feelings and nuzzles to start. And it’s a total of a year and a half before they are in a relationship.