The Forbidden Twins. (Twilight, Percy Jackson, Harry Potter)

explanation:

First off before I start this whole thing, I just want to make sure everyone knows this is the first time I wrote a Twilight/Harry Potter/Percy Jackson, crossover stuff I've always wanted to though but I could never think of something until now.

If you didn't notice, Sheila will be mated to Marcus and Seth Clearwater, and Caroline will be with Aro, Caius, and Jane. (I'm going to write a series of this book ((hopefully)) anyways the reason why I went ahead and wrote who their mates were is because I like it when characters date around before they meet their endgame instead of the whole love at first sight thing, although that kinda makes me a hypocrite, since I use that trope a lot. Although I'm going to try not to do that that much)

But before they meet their mates they will have boyfriends but Caroline will have a boyfriend and girlfriend.

Caroline's boyfriend and girlfriend: Fred Weasley, and Anna Crane Black ((Yes Sirius Black's daughter))《Fred and Anna both date her as a polygamous relationship Until Order Of The Phoenix  because when Fred leaves school he breaks up with Caroline, him and Anna stay together,  and the relationship between Fred and Anna becomes an open relationship》

Sheila's boyfriends: George Weasley, and Cedric Diggory ♡ Cedric first then George.♡

And their mother's name was Eloise Turner Gaunt, in this Merope (aka Tom Riddle's mother) had a sister whom had a daughter named Eloise, Eloise's mother was named Mellory Florence Gaunt met and fell in love with Hades, which led to giving birth to Eloise.

Caroline's hogwarts house: Slytherin

Sheila's hogwarts house: Gryffindor

I probably should have waited to tell you their houses but oh well.

I'm sure you know Sheila's father because of the cover but in case you don't I'll say it later.

Their names are:

Caroline Elle Cullen
Sheila Alex Cullen-Jackson

Carlisle and Esme adopted them both because their mother was his and Esme's mate, Eloise asked him to let Sheila live with someone that she knew and had became friends with back in New York she told him that Shelia was a little different to Caroline and that she would need to be with someone whom would be more able to understand her better, Eloise and Carlisle went to New York where Carlisle had met Sally Jackson and they explained to her about everything except for the fact that her sister is a half vampire part, and asked her to keep the Cullen last name.

Sally did just that but she thought that if she kept her that it would endanger her son so she took Sheila to Camp Half-Blood after Carlisle left, and Chiron met Sally at the border and asked him if it was possible for him to take her once she's three and he nods and Sally went back home and did just what she said she would and took care of her until she was six and Chiron came and picked her up.

Caroline went to New York, for a little while to see her sister she went to camp Half-Blood from time to time since she was a legacy of Hades she could walk through the border, she was also taught to fight, this was before she went looking for answers to see if there was different vampires.

Eloise had went to England with Carlisle and Esme and got married to them that way the Gaunt name would now change to Gaunt-Riddle-Cullen.