If Jon meets Rhaegar, it could change the story drastically. For one, Jon might gain a new understanding of his Targaryen heritage. He could learn secrets about his family that were lost over time. This new knowledge could influence his decisions regarding the Iron Throne and his relationships with other characters.
Missandei could be a member of Jon's harem. She is intelligent and well - educated. Her knowledge of different languages and cultures could be very useful for Jon. Additionally, Brienne of Tarth could also be part of it. She is a skilled knight, and her sense of honor would make her an interesting addition. She could be the protector within the harem and also offer her military expertise to Jon.
Yes, there might be. There are numerous fanfiction platforms out there like Archive of Our Own (AO3) where such stories could potentially exist. You can try searching on these platforms using relevant keywords to find it.
Jon's origin story is quite complex and involves a series of events. He was born into a certain family with specific circumstances that shaped his early life.
Jon Kent's age varies depending on the specific comic storyline and continuity. But generally, he's often depicted as a teenager or in his early twenties.