MirDaGoat567
In this AU, the Viltrumites and Gem society coexist. But to expand their respective empires, they have to colonize planets. So this is bound to cause tension, so they are enemy alien races. (NOTE: The Diamonds are still the most powerful beings in the universe in this AU.) So while at war, they capture each other's soldiers. Viltrumites just shatter captives because they don't really need them, but Gems don't. They put the captured Viltrumites in like a human zoo of sorts, and this causes Viltrumites to be born into Gem society.
Nolan is one of these Viltrumites born into captivity, and he's a strong fighter, and he was personally taught in Yellow Diamond's court. (NOTE: The reason Viltrumites are useful to Gems is because they are organic and just more durable.) Now onto the actual story. After Pink breaks her first Pearl, Yellow and Blue think she still needs a helper, but it can't be something that she can break with a scream (basically not a Gem). So Yellow and Blue pick Nolan to basically act as a Pearl/personal bodyguard to Pink whilst she doesn't have a Pearl.