When Pepe stepped out of his VW Beetle, the smell of the basurero and the heat of the fires were what he'd imagined Hell would be like – only he hadn't imagined children working there.”
-- Narrator (Chapter 1, Lost Children paragraph 15)

Importance: Brother Pepe arrived at the dump – or basurero – for the first time when he was delivering books to Juan Diego. He is religious, which is probably why he compares the place to Hell. The fact that children were working in such horrible conditions provides an important look into the lives of Juan Diego, Lupe, and the others who lived there.

But you're someone else. You're not always going to be Juan Diego Rivera – that's not who you are,' was all Lupe would say about it.
-- Lupe (Chapter 4, The Broken Side-view Mirror paragraph 58)

Importance: Lupe and Juan Diego were talking about Rivera and the possibility that he could be Juan Diego's father. Lupe said that Rivera was a kind man who loved them both...