It could be that Percy's relationship with a certain god or goddess goes horribly wrong. Say he offends Aphrodite in a way that she convinces the other gods to disown him. Percy then has to struggle not only with the loss of his divine family but also with the isolation from the demigod community that follows such a disownment.
It could be a jealous demigod. Maybe someone who has always been envious of Percy's popularity and power. This demigod could spread lies about Percy that lead to his disownment, making them the main antagonist.
One possible scenario could be Percy being disowned because of his powers being seen as too dangerous. Maybe the other demigods or even his own family in the fanfic fear what he can do and decide to cut ties.
Well, it could be that Percy has done something that goes against his family's values or rules. Maybe he's made a choice in his relationships or his actions that his family deems unacceptable, like befriending the wrong people or getting involved in a dangerous or taboo activity. And as a result, they disown him, leaving him to fend for himself and figure out his new place in the world.
There could be a rival within the family. Someone who wants Percy out of the way, perhaps for inheritance reasons or because they're jealous of Percy's abilities or popularity. This rival could be the one who instigates the events that lead to Percy's disownment. And then there might be a mentor - like figure outside of the family who takes Percy in after he's disowned and helps him to grow and face his new situation.
It could also be an ancient prophecy that is misinterpreted. The Oracle might give a prophecy that the gods misunderstand as Percy being a threat. So, in an effort to prevent the prophecy from coming true in what they think is the wrong way, they disown him.
Well, I'm not sure of the exact titles, but a good 'Percy Jackson disowned' fanfic would probably explore Percy's emotions deeply. It could show him feeling betrayed by his friends and the gods. Maybe it would have him going on a solo adventure to prove his worth. He might encounter new allies and enemies in the process. It could also be interesting if the fanfic explored how the other demigods reacted to his disownment, whether they supported him or not.
You can start by looking on fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. These platforms have a large collection of fanfics, and you can simply search for 'Percy Jackson disowned' in their search bars. There are also some Percy Jackson - focused fan communities where fans might share their own 'disowned' fanfics or recommend ones they've read.
Percy would be extremely angry. He loves his mother deeply, and her disownment would feel like a huge injustice. He'd probably want to immediately go and confront the people who disowned her. Maybe he'd also feel guilty, thinking it's his fault as a demi - god that his mother is in this situation.
I'm not sure specifically as there could be many different takes on it. It might be a fanfiction where a character named Percy is disowned by his family or group. It could explore themes of isolation, self - discovery, and dealing with rejection.