Well, for Henry fanfiction, it depends on what aspect of Henry you are interested in. If it's a Henry from a particular movie or book series, search for that specific tag along with his name. For example, if he's a character from a fantasy world, fanfictions might delve into his adventures in that world, his friendships, or his struggles against the antagonists.
A fanfiction might depict Henry and Violet as time - travelers in the 'Once Upon a Time' universe. They accidentally travel back to the time when the first dark curse was cast. Here, they have to be very careful not to change the past too much, as it could have a disastrous effect on the future. They meet some of the original characters from the show and try to work with them to stop the curse from ever being cast in the first place.
Well, without having read the 'Once Upon a Time Henry and Violet' novel in detail, it could be that Henry and Violet are facing some sort of challenges. Maybe they come from different backgrounds and society is against their union. Or it could be a mystery where they are trying to solve a crime that has some connection to their families. The story might also be about their self - discovery journey as they grow and learn more about themselves and each other.
You can start by looking on fanfiction websites like Archive of Our Own (AO3) or FanFiction.net. These platforms have a vast collection of fanfictions. Just use the search bar and type in 'Henry and Cinderella Once Upon a Time' and you should get a list of relevant stories.
One common storyline could be that Henry's sister discovers she has a special power. For example, she might be able to control time like in some 'Once Upon a Time' scenarios. This power could either be a blessing or a curse as she tries to fit into the world of Storybrooke. Another storyline could be her exploring her family history. Since Henry's family has such a complex backstory in the show, she could be on a quest to learn more about her parents and how they came to be in this strange world. And sometimes, she could be involved in a love triangle with some of the other characters in town, adding a romantic and dramatic element to the fanfiction.
If it's a fictional Henry, perhaps the common themes could be the journey of self - discovery through love. Henry might learn about his own desires, strengths, and weaknesses as he experiences different relationships. Also, themes like sacrifice and the power of true love could be present.
One common theme could be self - discovery. Henry might be exploring his identity in a world full of magic and different relationships. Another theme could be forbidden love, as in the original 'Once Upon a Time' there are many complex relationship dynamics that could be adapted to a gay relationship involving Henry.
One possible plot could be Henry discovers a hidden connection between himself and Cinderella. Maybe he finds an old spell book that reveals a prophecy about them working together to save the Enchanted Forest from a new dark curse.
There are fanfictions where Henry Mills time - travels. He could go back in time and meet his younger self or his ancestors. In one such fanfic, he goes back to the time when Snow White and Prince Charming first met and accidentally changes something in the past. This then creates a whole new set of challenges for him to fix in the present to restore the original timeline. It's a really exciting concept that plays with the time - travel trope in a 'Once Upon a Time' context.