Family Strain

My husband’s 35 year old son is a heroine addict. Says he has been clean for 5 years, but many problems have developed from this addiction such as he has been unemployed for the past 7 years, and has been asking and getting money from his father.  His father is an enabler and cannot say no to him no matter what he asks.  How do I stay in this relationship and not go insane?  We have been married for 14 years.