There are books with this as a title and I'm not singularly picking out any book and criticizing on it. I'm just going through the cliches these books have.

There are roughly about 9.9 K Weasley sibling stories on Wattpad. And almost all follow the same plot line. However there are a few changes here and there such as the Weasley sister's origin:

a) She is either Ron or Ginny's twin who was simply ignored and forgotten. Until she starts school at Hogwarts.

b) She is not a Weasley biologically but is adopted by them. Probably the daughter of famous Aurors who died during the war and now their kid lives with the Weasleys. 

c) She is a Weasley but attends Beauxbatons or some other school and mysteriously shows up at Hogwarts for no particular reason whatsoever. Only explanation ever given is that she's a transfer student.

OC's Personality and Plot Facts:

1. The Weasley sister obviously has red hair like the other Weasleys but she is far too good looking to be considered one of them. The adopted Weasley can have differing appearance and can have hair color other than the Weasley red.

[If she is adopted by the Weasleys, no reason is given to that. I mean, it's hard enough for the Weasleys to bear the expenses of their already large family, so there should be a specified reason why they would go and adopt someone else as well, Also if it is a story of the transfer student case, why would this Weasley girl be studying in Beauxbatons while the whole of her family went to Hogwarts?]

2. For some untold reason, this Weasley sister is neglected by her whole family (quite like the case with Other Malfoy stories) and even though the concept is illogical still you can see in many Weasley sister books that the poor girl gets hated and tormented by her family.

3. If she studies at Hogwarts, she gets sorted in any other house except Gryffindor or Hufflepuff which makes her family hate her even more. And if it is a transfer case, she comes to Hogwarts at the time of the Triwizard Tournament.

[Hufflepuffs need to be recognized, I think I might have said this a lot but still. The Badgers deserve to be represented].

4. She becomes the star student of Hogwarts and is the favorite of every teacher there ever was. But thankfully, this once Snape is not included on the list.

5. And since she is such a ravishing beauty, she captures the hearts of every boy who ever studied at Hogwarts during her time at school.

6. But she falls in love with either Harry or Draco or Cedric or all three of them depending on the author.

[I hate love triangles let alone love quadrilaterals. I mean... I'm not against anyone for that but you know what, it creates such unwanted drama that it is bound to distract the reader from the story altogether and just keep focusing on who they are going to end up with].

7. Her school life is fabulous because she is so admired by everyone and her siblings are so jealous of her.

8. But at home, her life is nothing short of hell where Molly becomes Elizabeth Bathory and Arthur becomes the malicious Adolf Hitler.

[All of you know Hitler, but many are still wondering on who Elizabeth Bathory is. Elizabeth Bathory was a countess who lived in the Carpathian Mountains and her nickname was Countess Dracula. She was possibly the most prolific serial killer in history responsible for the killing of 650 girls in whose blood she used to bathe, thinking it made her younger and beautiful. Disgusting, I know].

9. However, she joins the Order, fights against Voldemort and helps the Trio win the war.

10. In some stories, this Weasley Sister is the one who destroys the Slytherin Locket or any other Horcrux and becomes a widely acclaimed hero. And she gets her happily ever after with whoever is the love of her life.

Effects On Other Characters:

1. The characters most bashed here are all of the Wealseys. Literally. All... Of... Them.

2. Arthur and Molly can simply not be abusive parents. And they are portrayed as the worst parents which makes me feel thoroughly angry. Arthur and Molly cared for Harry just like they cared for Ron. Why would they treat any of their children like that?

And when I read such stories, I can understand how the movie directors could have made Helena Bonham Carter so angry in this scene:

[Literally, my state after reading about an abusive Weasley family].

3. Ron is portrayed as a selfish and mean person who tags along with Harry just for fame. And that is so so wrong. Ron stood up to Sirius when he thought Sirius was going to attack Harry. He stood up on his broken leg and challenged Sirius Black (who was widely known and feared as a mass murderer) that to kill Harry he would have to go through him first.

4. Ginny is also either never shown much in the story or just portrayed as a one dimensional bitchy character who is rude to everyone and has a huge inflated ego.

[I may not be a great fan of Ginny Weasley but please don't portray her any worse than what she already is].

5. Depending on who the OC is dating, the other person in love with that canon character is also ruined.

6. If she's dating Harry, then obviously Ginny is a mean person.

7. If she's dating Draco then Pansy is a jealous and hypocritical bitch. 

8. If she's dating Cedric, then Cho becomes the ultimate hater.

9. But Hermione's character also is ruined way too much even though there is no apparent reason for that. And all her shining moments and dialogues are given to the OC.

10. Also if she's dating Draco then he does a full 180 degree flip and turns into a sensitive and caring person who is just widely misunderstood and bullied.

[While in reality, everyone wanted Hermione to do exactly what she did to the evil little cockroach in her 3rd year].

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Exception:

If you want a light and humorous read regarding the adopted Weasley sister, you can check out The Veil Of Time by Viola130831 . It is the first book in her Veil Trilogy and focuses on the book plot and is written in the Weasley sister's point of view. The fun aspects are tackled really well in the book and Fred and George are the heart and soul of each chapter. Plus, this Weasley is not a younger sister of Ron's who falls for Harry or Draco, she is about the twin's age and is just as fond of pranking. The writing style is casual and I'm sure you will love it.

I'm guessing that over the years, the book will get serious as it will deal with the war and upcoming years but you will have to see it for yourself when the remaining books in the trilogy get posted.

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Stay tuned for the next update!