The story begins a looong time ago... Merope Gaunt was a really good witch... back in that time, families needed to have a son, to be the heir, first born girls wasn't treated well... that's why Merope needed to be very clever... when she gave birth to her first child and found out that it was a girl, she did everything to protect her
The first problem was the father...
He was expecting a baby, he saw the "clues" on his wife...
If he found out that the baby was a girl, to avoid the shame on the rich family he would have killed her.
So she told him the baby was born death and hid her far away from the father
few years later Merope got pregnant again, this time giving birth
to a healthy boy
She named him Tom Riddle, after his father...
About half a year later, she told the husband that she was a witch and she has been giving him love potions... he left her
What they didn't know then that she was pregnant again...
Later when she noticed it, she also got to know something else: she got a magical disease... she was getting weaker, her magic getting less every week
...she was dying...
She would die
when she gives birth to the 3rd child, if not
So, she did what she's been doing for years now: protected her children.
She loved her son the most, because he reminded her to her beloved husband
So first she took care of him
She disguised herself and visited the nearest orphanage, said she's from a nearby orphanage that is being closed and the boy needs to be taken to another orphanage
She told them that the mother died, the kid's name it Tom Riddle
Then she left and never returned...
She wanted to do the same with the girl too
But she was too late... the 3rd children was early but she was too week
She died after giving birth to her 2nd daughter...
The kids were found in the house she hid
They were taken to an orphanage together... not the one their brother was in... no one knew their name so they called the younger Amelia and the older Amanda, after the woman who found them.
We all know little Tom's story
So let me talk about the girls...
2 families adopted them... separately...
Both of the families moved abroad
taken to America
Amelia was taken to Russia
Amanda was magical... but it took her long to show it... when the muggle parents noticed they tried to get rid of her
She escaped from the family
wizarding village and started learning
She mastered the dark arts
And then she went back to find her real family
She found her
father...dead... killed by her brother
After long searching, she found him
She was an animagus, so she could join her brother without notice
Amelia in Russia was adopted by muggles too
But her magic showed really early
gave her in an orphanage when they noticed
But the family's neighbors were magical and they noticed the girl's talent, so when they found out where's she, they adopted her
They were dark wizards
Trained her with dark magic too
Then sent her to Durmstrang
There she was chosen to the few who were sent to Hogwarts to the tri-wizard tournament
She heard about a powerful dark wizard there who just came back to life and wanted to join him...
...and she finally met her family
Harry Potter "killed" Voldemort, Nevil "killed" Nagini
But Nagini was Amanda's animagus form and, as a clever dark witch, she had horcuxes too
So neither one died
Amelia took her siblings'' souls to America and studied the dark arts to bring them back to life