Perhaps there's a curse that has been placed on the Great Hall. It makes the food turn into strange and sometimes dangerous things. Harry, Hermione, and Ron take it upon themselves to break the curse. They start by researching in the library, but soon realize that they need to explore the Great Hall more closely. They discover that the source of the curse is an old grudge held by a former house - elf who used to work in the hall. They then have to find a way to make amends and break the curse.
In a fanfiction, the three of them could be in the Great Hall for a sorting ceremony that goes wrong. A new student's magic is so powerful that it disrupts the normal process. Harry, Hermione, and Ron step in to calm things down. Hermione uses her vast knowledge of magic to try and control the situation, Ron's loyalty and bravery encourage the other students not to panic, and Harry's natural leadership helps them come up with a plan to contain the new student's magic until the teachers arrive.
One plot idea could be a magical adventure where the four of them go on a secret quest together. Maybe they discover an ancient magical artifact that requires all their skills to unlock its secrets. Another could be a time - travel plot where they end up in a different era of the wizarding world and have to adapt and work together to find their way back.
A really interesting plot could be that right before the wedding, a dark wizard from Ron's past tries to disrupt it. Hermione and Ron, along with their friends, have to fight off the threat while still making sure the wedding goes on as planned. It would add a lot of action and adventure to the fanfiction.
One idea could be that they are adopted by a powerful but reclusive wizard. This wizard has his own motives for taking them in, like using their potential for a grand magical plan. Another plot could be that they are adopted into different families at first and then reunite later, realizing they have a special bond that goes beyond blood relations. Maybe they discover that their adoption was part of a prophecy protection mechanism, to keep them safe from the dark forces that are after them.
One interesting plot is when the Great Hall is turned into a magical maze for a special event. Harry and Hermione have to work together to get through it. Along the way, they face different magical creatures and challenges, and it really tests their friendship and magical skills.
One plot idea could be that Ron and Hermione accidentally discover a hidden passage in the Chamber of Secrets that leads to an ancient wizarding library. In this library, they find a spell book that has the power to reverse dark magic spells, which becomes crucial in fighting the basilisk's venom. Another idea is that they get trapped in a part of the Chamber that has a time - warp effect, and they have to figure out how to get back to their own time while also dealing with the threats within the Chamber. And a third idea could be that Hermione gets cursed by a relic in the Chamber, and Ron has to go on a solo quest to find the antidote while also protecting Hermione from the lurking danger of the Chamber's secrets.
One idea could be exploring how they handle their kids' magical education. Maybe one of their children has a special ability that requires unique teaching methods. Another could be a story about a family vacation where they visit a new and mysterious magical place and encounter various adventures. Or perhaps a plot where they have to deal with an old enemy from their Hogwarts days who resurfaces and targets their family.
One idea could be that Ron and Hermione accidentally stumble upon a secret passage in Hogwarts while investigating the mystery of the Prisoner of Azkaban. This passage could lead them to a hidden chamber where they find clues about Sirius Black that no one else has discovered yet.
One plot idea could be that Hugo has a unique connection to time - turners. Since Hermione was so involved with time - turners in the past, Hugo might inherit some strange ability related to them. Maybe he accidentally sends himself back in time and Ron and Hermione have to figure out how to get him back.
A possible plot is that they are in bed and start arguing about a minor thing like who left their wand on the wrong side of the bedside table. But then it turns into a playful banter and then a passionate moment as they realize how silly the argument was. Another idea is that they are in bed getting ready to go to sleep and they start talking about their families. Hermione tells Ron about her Muggle parents and how she misses them sometimes, and Ron shares stories about his large family at the Burrow. This conversation deepens their bond as they fall asleep in each other's arms.