As I'm sure the majority of you all have seen 'Harry Potter's Twin' or 'Hermione's Twin' or 'Random Character's Twin' seems to be a very common and popular theme for fan fictions on Wattpad. Which isn't a bad thing, in my opinion, it's just the fact that there is so many of them and most of them have the same 3 plots. I'm using the character Emily who is Harry's twin as an example just to make things easier.
1. Emily is Harry's twin she lives with him at the Dursley's but the twins are in no way like each other. Emily and Harry go to Hogwarts where Harry is placed in Gryffindor and Emily in Slytherin. Emily becomes best friends with Draco Malfoy and Harry, Ron and Hermione hate her. While her brother and his friends are off on their adventures Emily falls in love with Draco. When her brother is about to find the Philosophers Stone/ go into the Chambers of Secrets/ go to see Buckbeak die etc etc Harry and his friends realise "Hey we don't know how to do any spells what so ever. So let's ask Emily to help us!" They ask Emily for help she agrees but she makes it clear that she still hates them. Harry, Ron and Hermione cannot do any spells for some reason and Emily saves the day.
2. When Lily and James got killed Emily was whisked away to France, she was told by her adopted parents that she was Harry Potters twin. She goes to Beauxbatons for a few years then in her fourth year she goes to Hogwarts for the Triwizard Tournament she meets Harry and is very excited Harry however does not know who she is. Emily then proves that she is his sister and everyone is happy. When the champions are being chosen Harry and Emily's name come from the goblet. Emily falls in love with someone (usually Cedric or Draco). And when it is the final task Harry, Cedric and Emily all go the graveyard. If Emily had fallen in love with Cedric she is devastated by his death. When Voldemort has his body back Emily does some really advanced magic and saves the day!
3. The only friends Emily has is Harry, Ron and Hermione but they don't talk to her very much, Emily basically just follows in their trail hoping that one day they will include her. When Harry and his friends are about to go on a dangerous adventure Emily wants to go with them but Harry says "No Emily you're too young and helpless you must stay here," Emily is very sad. While off on their dangerous task Harry, Ron and Hermione are about to die, when who should come along and save the day? Emily of course! She saves their lives and they all become best friends.
So yeah that's what I believe to be the three main plots that the twin stories have. Now I'm not saying that these are the only plots there are these are just the ones I've seen the most, and although some have been bad a lot of them have been really good! I hope you enjoyed this chapter!