You're not my sister!

January 7, 2001.
It was a very cold night. Light was walking home with his pregnant girlfriend. Suddenly they saw three children who were riding on a sled, they did not notice the young couple and hit them. Leila (light's girlfriend) woke up in the hospital, and Dr. Weissman was in front of her. He said to the young girl:
- Congratulations! You have a boy!
Leila answered him:
"What?" I... I... I don't believe it! On the ultrasound I was told that I have a girl!
"Oh, wait. There was a mistake on the ultrasound, you actually have a boy and a girl. We'll get it now!
After 7 minutes:
"Here's your daughter.
"Where's light?"
"Light, is this the father of your children?"
- Yes!
"I don't want to tell you this, but...
"What?"
"He was killed in a collision
- *starts sobbing*
January 17, 2016.
So came the birthday of light (Leila named her son after his father) and Dasha, arrived uncle, aunt, grandparents. Everyone was at the festive table and celebrated the 15th year of the children's lives. Suddenly light began to vomit. Light went to the toilet and when I looked inside the toilet I saw a note. He took it out and put it on the washing machine. When he vomited all the vomit, he took a note from the washing machine. There was a certificate of adoption Dasha. Light decided not to upset Dasha on her birthday, so he decided to tell her the truth the next day.
January 18, 2016.
Light called from his room Dasha sitting in the kitchen. The girl came to light's room and said:
"What do you want?"
"I need to talk to you."
"About what?"
"You're right...
"What am I doing?"
-reception.
Suddenly Dasha got mad, and tentacles came out of her back. She began to strangle light. Then she grew up to 6 meters, and her face began to turn gray, and her eyes, nose, ears and mouth began to disappear, and her everyday clothes turned into a funeral suit. And at that moment light's grandfather came into his room with a shotgun and said:
"GET THE FUCK OUT OF MY GRANDSON, YOU SOULLESS CREATURE!"
Slenderman looked at the elderly man, and was gone in a moment, and the bullets from the shotgun flew into the forehead of the teenager.
Source: https://kripipasta.com/story/10006-ty-ne-moya-sestra.html