I think the good son are those who followed Christ throughout their lives, and the prodigal is the apostate sinner who came late to salvation.
Much like the workers in the vineyard who were hired early, the good son grumbled that the latecomer was treated so well.
A very reasonable take on it—thank you. The alternative of Jews and Gentiles which I mentioned is also popular. Guess we’ll have to ask Jesus when we see Him.