The title is a serious reference to both the father and the son. The father has always been "the drunkard", and his alcoholism has caused both the mother and the son pain. To pay for his alcohol, the father has pawned items from the house. This is why the wife and son are so concerned when the father decided to go to the funeral, knowing that he will also go to the bar with his friends afterwards.
The humor in the story stems from the son's behavior when he's drunk. He is a mirror image of his dad when his dad is drinking. The father must take his son home before he can get drunk, and this is why the mother calls the son his father's "guardian angel".