When is it enough already when a parent constantly loans money to his adult son who never pays him back ?

My husband and I have only been married less than a year and even when we were engaged his son has always been a financial disaster. He calls, he loans him money and his son promises to pay it back and he never does...I told him as long as you keep bailing him out he will never stand on his own two feet and be a man. He is married and his wife appears to have the same problem..I didn't sign up to take care of two adults...He needs to wake up and smell the coffee...