Wikipedia wrote:

There also is a third alternate ending where Evan watches his own birth video when he is in the clinic, which makes him travel back in time to the moment of his birth when he was in his mother's womb. Evan decides to kill himself and thus he was never born. Without him ever being born, Kayleigh and her brother decide to live with their mom going on to have happy lives, and Lenny also grows up happy without Evan's destructive presence. Evan's mother later on had a daughter. Earlier in the film Evan's mother mentioned that she had three stillbirths before him. This suggests that their father's abilities were passed down to each of them and they all made the same decision in the end, to never have been born at all.