I'm guessing there's no chance that he killed them because they objected to his "borrowing" their car, right?
His mother may be pure as the driven snow, but I still think having her 13 year old commit double parricide and drive drunk on a school night reflects poorly on her.
His father is off the hook?
It is unclear by the article but what you wanna bet this was the in-laws talking bad about their daughter-in-law?
Either way they should not have said this to a 13 year old. He is too young to understand adult things and in his eyes Mom is everything.