City of Bones #4 - Obstacles that main characters run into

I'm reading a book called "The City of Bones" by Cassandra Clare and I finished the book (553/553 pages).

One of the obstacles that my main characters face (Jace and Clary) in the novel is that Jace and his allies who are half angels and half humans are trying to find the mortal cup. The mortal cup is a chalice that causes a human who drinks from it to become a shadowhunter (a person who hunts demons) just like Jace and Clary. The only problem is that Clary's mother hid it so that nobody could find it. Only Clary knows where it's hidden, but her mother put a block in her head so that she can't remember.  Here is a quote about this obstacle:

"There is a block in your mind, your memories cannot be reached". (Clare p.200)

One of the other obstacles that my main characters face in the novel is that Valentine, the evil shadowhunter, tells Clary and Jace that they are brother and sister. Clary and Jace are astonished and don't want to accept this fact because they love each other.  This is the quote in the book when Valentine presents this obstacle:

"My mother is alive?" said Jace "She is" said Valentine. "Alive, and asleep in one of the downstairs rooms at this very moment. Yes, " he said, cutting off Jace before he could speak,"Jocelyn is your mother and Clary-Clary is your sister". (Clare p.501)