One negative impact is that it can be offensive to many people. It may also distort the original characters if it is related to an existing story. And it may contribute to a less healthy and respectful fan culture.
Definitely not. Such content is not in line with the general standards of mainstream literature. Most works in mainstream literature aim to convey positive values, deep emotions or important ideas, while this kind of sexual fanfic mainly focuses on improper and often offensive content.
Consider their upbringing. If they were raised away from the main Lannister stronghold, they might have a different set of values. Maybe they were raised by a kind - hearted servant who taught them to be more empathetic. So their personality could be a mix of Lannister pride and this new - found empathy. They could be conflicted between loyalty to their family and doing what is right according to their own conscience.
Sure, many fanfiction authors like to play around with different character combinations and scenarios. Jaime Lannister is a complex character, and Lyanna has her own allure in the story. The idea of her being pregnant in a fanfiction involving Jaime could be used to explore themes like love, honor, and the consequences of actions. It might show how these two characters from different houses and storylines interact in such a situation.
One possible plot could be a young Lannister male OC who, unlike his power - hungry relatives, is more interested in the arts and knowledge. He could secretly befriend a maester and learn about ancient Valyrian lore. This would put him at odds with his family as they see his pursuits as a waste of time. He might then use his knowledge to try and broker peace during the war, facing many challenges along the way.
Power is a very common theme. Since Tywin is all about power in the original story, fanfictions often explore how he gains, maintains, or loses power in different scenarios. Family dynamics is another one. His relationship with his children, especially Tyrion, Jaime, and Cersei, is always a rich area for exploration in fanfictions.
Tyrion Lannister was married to Sansa Stark. It was a union that was arranged for political gain. Sansa was a young girl who had already endured much trauma, and this marriage was another blow. Tyrion, on the other hand, was a complex character. He had a sense of justice and kindness that set him apart from his family, but he was still a Lannister. Their marriage was a strange mix of mutual understanding in some aspects and complete incompatibility in others. As the political situation in Westeros became more volatile, their relationship became even more strained, and ultimately, they went their separate ways.
I have no clear idea. It might have been taken down due to copyright concerns or maybe the plot just reached a natural conclusion that wasn't well-received.