The way the Fidelius Charm works is that the spellcaster chooses one person to be their secret-keeper.
However, this decision ended up leading to their tragic fates.
Pettigrew was definitely a poor choice for a secret-keeper, even before he revealed his traitorous ways.
His true character could be inferred by his Animagus form: a rat.
Even apart from that,James and Lily should have picked someone more separate from them.
In some ways, Voldemort was smart in his desire to never trust anyone.
Of course,that isn’t to say that Voldemort was completely safe from betrayal.
