LvWrAM123--Thank you for your input. "Managing" an addiction would first require someone to acknowledge they have an addiction. In the case of my young cousin, he's willing to admit he "makes bad decisions when he drinks" and he has "addictive tendencies" but continues to abuse/use a variety of substances. His mother has enabled him for years and continues to do so, although she acknowledges he has a "substance abuse problem".
As for our part? My husband and I have sufficiently communicated our concern/regard. What else can we "do"?