Can guardians of a 17 & 15 yo. both be charges w/ permitting unauthorized minor to drive?

my 17yo nephew was charged with dui and mip (he has no license) but his mother was not charged for permitting unauthorized minor to drive and when my 15yo was stopped while taking a friend home she was charged with no drivers license and i was charged with permitting unauthorized minor to drive. is there a difference cause of the age?