Well, perhaps in the fanfiction, their son could be a key figure in preventing a great war. He may inherit some of his father's strength and his mother's political cunning. He uses these traits to unite the warring factions in Westeros. For example, he could broker a peace deal between the Lannisters and the Starks, using his unique position as the heir of both houses in a sense.
In this fanfiction, their son might be a reluctant heir. He could be more interested in the arts or in exploring the world beyond the politics of the Iron Throne. However, due to his birthright, he is constantly pulled into the power struggles. He has to face challenges from other claimants to the throne, and in the process, he might learn to embrace his role and bring about a new era of peace and prosperity in Westeros by implementing new laws and promoting equality among the different regions.
One possible plot could be that their son discovers the truth about his parents' tumultuous relationship. He might struggle with the knowledge that his mother had affairs and his father was not the ideal man he seemed. This could lead him on a journey of self - discovery, trying to figure out his place in the Seven Kingdoms.
One possible plot could be the son growing up in the shadow of his mother's power-hungry ways. He might struggle with the expectations placed on him due to his family name. For example, he could be groomed to be a political pawn but secretly desires a more peaceful life away from the power struggles of King's Landing.
The son's character might develop as he uncovers family secrets. Knowing about his mother's true nature and his father's misdeeds could make him question his own identity. He could start as a naive young man, but as he digs deeper, he becomes more cynical. But instead of being consumed by it, he decides to break the cycle of corruption and lies that his family has been part of. He could start to develop his own moral code, different from the cut - throat ways of his parents.
Perhaps in the fanfiction, Cersei's son discovers a hidden power within himself. He uses this power not for domination like his mother would, but to heal the broken kingdom. He might travel across the land, learning from the common people and using his new - found abilities to bring prosperity.
One possible storyline could be that Cersei's daughter rebels against her mother's tyrannical ways. She might see the destruction Cersei has caused and decides to take a different path, perhaps allying with the Starks to bring peace to Westeros.
One possible plotline could be Cersei's son growing up to be a more benevolent ruler than his mother. He could see the destruction she has caused and try to make amends. Maybe he forms alliances with former enemies to bring peace to the Seven Kingdoms.
One idea could be a fanfiction where Robert Baratheon's son, perhaps Joffrey (even though he was a cruel character), has a change of heart. In this fanfic, he could start to see the error of his ways after meeting a wise old maester who tells him tales of great but just kings. He then tries to make amends for his past actions, which would be a huge departure from his original character arc in the show and books.
In an interesting fanfiction plot, Cersei's son could be exiled from King's Landing. During his exile, he forms a band of outcasts. Together, they build a new community away from the power struggles of the capital. As he grows, he realizes that his mother's way of ruling is wrong. Eventually, he returns to King's Landing with his new - found wisdom and tries to overthrow his mother's tyrannical rule, not to take over but to establish a more democratic and fair system for the people of Westeros.
He could influence events by being a voice of reason in Cersei's court. If he's intelligent and perceptive, he might be able to persuade his mother to make more diplomatic decisions rather than always resorting to force.
One possible plot could be that Naruto, as Cersei's son, grows up in the world of Westeros. He might have to deal with the political intrigue and power struggles there. Since Naruto is known for his determination, he could try to bring about change in the often - cutthroat world of Westeros, perhaps using his ninja skills in a new and unexpected way.
In a 'Game of Thrones Epilogue Fanfiction', it could be about the adventures of the next generation. The children of the main characters might discover new threats or mysteries. For instance, they could find hidden secrets about the White Walkers that were not fully explored in the original series, leading to a new quest.