Annie Shan

Annie Shan is Darren's younger sister and the mother of Darius Shan. Her parents are Dermot Shan and Angela Shan. She returned in the 11th book (Lord of the Shadows). She had a child with Steve Leonard and he was named Darius Shan.

Cirque Du Freak (book)
Annie Shan and Darren always got on well, but when the Cirque du Freak came to town she wanted to go instead of Darren, but she asked Darren to bring her a souvenir. After Darren had stolen Madam Octa, she came in Darren's room and saw Madam Octa and screamed. The Spider then bit Steve, paralysing him.

Cirque du Freak: The Vampire's Assistant
In the movie, no mention is made of Annie ever knowing anything about the Cirque until she is kidnapped along with the rest of her family by Murlough and Steve. Later on in the Darren Shan books she has a son with Steve and darren bloods him to make him a half-vampire like him