The Unborn (2009)

This is my other favorite horror film.

Casey Beldon (Odette Yustman) is being haunted in her astonishing dreams with a mysterious looking dog and an evil child with blue eyes.

After being hit by a mirror with her neighbor's son, Casey's eyes started to change the color. She goes to the opthalmologist and the doctor explains she she has a twin sister or a brother. Because the genes may usually occur in twins.
She later asks her father if she has a twin and her father revealed that her twin bother died in her mother's womb.
She discovers a letter that addressed to Sofi Kozma and a picture belonged to her mother.
Sofi told her everything that she is the ultimate survivor of the experiment during the Holocaust and that she is her grandmother. She warned her to be careful because she is in great danger.