It is a story that provides two sides of the same coin.
Brothers. They grew up in the same home, same opportunities, same blessings, same curses, same father.
And yet …
The story opens with one brother (the younger) wanting his share of the estate (Luke 15:12). So what the son is asking is if he could have his inheritance … remember, the son’s father is the one the son is asking … his father is still alive. How ludicrous to ask for ones inheritance from the parent, when the parent is not dead. What the son is asking is not for his inheritance, but he wants a third of father’s estate, his father’s worth, as the father is not yet dead. He is asking for what is not yet his.
(a third, as the younger son, he would receive a third of the estate and the elder brother would receive two thirds).
And Jesus (who is telling the story) says that the father divided his property between them (v.12). No note of hesitancy or discussion, for what the father felt about this request is immaterial to the story, only that he fulfilled the request of the son (though, the recording of his waiting for his son to return, later in the story, is very relevant).
Then, in two short sentences, the predictable result of the son’s demand is that his inheritance is gone … by his own misuse of what his father gave him.
It was not until his life hit it’s lowest, surrounded by pigs in their slop, that he came to his senses (v. 17) and realized the hedge of protection he would be under as a servant of his father … perhaps he then realized the hedge of protection he had always been under as the son of his good father.
So he journeyed home. Upon reaching the city gates, a man was approaching this wayward son, approaching in a run. His father had been waiting for him. His father knew, predicted, the folly, the poor decisions that the son would get into. And as the son humbled himself (perhaps for the first time in his life) and admitted that he had sinned against heaven and against his father (v. 21).
But, the father, responded as a father filled with love, a father who knew that loving means there will be mistakes, for love is a always a choice, declared, this son of mine was dead and is alive again; he was lost and is found (v. 24).
And a celebration breaks out.
The end …
NOT!
For that is only half of the story, that is only the story of one son. This is the story of two sons.

While a welcome back party was going on at the home, the older son had been in the field (v. 25) … we presume he was working in the field. You know … doing what he was supposed to be doing.
When this older brother heard the reason for the celebration, he didn’t just simmer, but he became angry and refused to go in (v. 28). Basically, his knickers were firmly in a knot and he was done with following the formula of how to be a good son. Done with his spoiled little brother. Done with breaking his back, doing what was expected of him. Done with being the dependable son, the faithful son. Done with doing it all right and yet, not being celebrated for his choice to follow the rules.
When his father went out and pleaded with him (v. 28), when his father showed the older brother his face, it it then that the older brother spoke what was really on his heart (and, no doubt was in his heart for years):
‘Look! All these years I’ve been slaving for you and never disobeyed your orders. Yet you never gave me even a young goat so I could celebrate with my friends. But when this son of yours who has squandered your property with prostitutes comes home, you kill the fattened calf for him!’ (v. 29-30).
And now we see that the root of the problem has nothing to do with his younger brother, but pride.
I have been slaving for you … I is a mighty powerful word. It declares independence. It is as though the older brother is declaring (much like Frank Sinatra) I did it my way … except along with the proclaimed independence, he announces his motivation … slavery … slaving for you. This brother has not been good, or responsible, or faithful, or hard working out of love and respect for his father, but out of obligation.
This, elder brother had a firm belief in one thing …
his rule-keeping
his obedience
his works
This tale of two sons, two very different sons who entered a life where they both received the same opportunities, from the same loving father. But, only one son is the prodigal, because only one son recognized that he had sinned against heaven and against his father (v. 21). Only one son realized that he could not save himself.
The one son … his were sins that led him to see himself as bad for the bad things he had done.
The other son … his were the sins of believing he was good because of the good he did.
“I have taken all my good deeds, and all my bad deeds, and have cast them together in a heap before the Lord, and have fled from both to Jesus Christ, and in him I have sweet peace.”
David Dickson
(on his deathbed)