Welcome to SR......it is nice to have a place to talk about issues with others who understand.
Although you can't control your parents, there is no harm in sending them a gift. Send them a copy of "Codependent No More" by Melody Beattie. Maybe......just maybe....they'll read it and see themselves.
It is hard being the parent of an addict. The denial and desire to protect your offspring runs very deep and is hard to penetrate. If their son is in rehab right now and the facility has a family program, encourage them to go. That is where I "woke up" about my son. Recovering addicts and alcoholics got through to me when nothing and no one else could.
gentle hugs
ke