Complex sentence: There are only two incidents where the Fidelius Charm is used in the Harry Potterseries the first is when Lily and James Potter (Harry's parents) are hidden with this charm with Peter Pettigrew as their Secret keeper, who betrayed them.
Split into simpler sentences: There are only two incidents where the Fidelius Charm is used in the Harry Potter series. The first is when Lily and James Potter (Harry's parents) are hidden with this charm with Peter Pettigrew as their Secret keeper, who betrayed them.