From another perspective.
That parable can be viewed in two ways, the parable of the “two brothers” or the parable of the “waiting father”.
I would keep in mind the principle not subject to change, no man can come(impossible) to the father unless he first enables them, and if they do come he will in no way cast them out. He finishes that which he begins in us to the end.
Philippians 1:6 Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:.
Either Christ does all the work of dsavation or he does nonne.
Looking at it from the standpoint of the waiting father as to the context , it came after the last of the previous chapter when Christ said. “For which of you, intending to build a tower, sits not down first, and counts the cost, whether he have sufficient to finish it?” And said "he who has ears let Him hear"
Those who did count the cost of the waiting father He drew near. The sinners who knew they were sinners showed they were given ears to hear.
Luk 15:1 Then drew near unto him all the publicans and sinners for to hear him.
The self-righteous ones being angry at God as to those who were not given ears to hear,not only looked for fault in others put Christ in the same class as the sinners.
And the Pharisees and scribes murmured, saying, This man receiveth sinners, and eateth with them.And he spake this parable unto them, saying, Luk 15:3
Three series of parables ending with the prodigal son or the waiting father.
Having sent a famine of the land the son having come to himself realized as the father worked in Him to both will and do his good purpose it was also a famine for hearing the word of God the father ,even the slaves having an a superabundance of bread. Bread representing the word of God in that parable
`And having come to himself, he said, How many hirelings of my father have a superabundance of bread, and I here with hunger am perishing! having risen,(The drawing of the father ) I will go on unto my father, and will say to him, Father, I did sin -- to the heaven, and before thee, Luk 15:
Having been turned by the hearing of faith he could then repent .This shows us God does all the work of salvation. The older saw no need to repent, refusing the voice that could turn him, like Cain, never entered the relationship . Therefore the favor of God (grace) was supplied to the one that did have ears to hear which did turn Him to the waiting father. The older like a as a bullock unaccustomed to self righteous, the yoke of sin, did not hear the voice that could turn him so that then after he was turned, he could repent.:
I have surely heard Ephraim bemoaning himself thus; Thou hast chastised me, and I was chastised, as a bullock unaccustomed to the yoke: turn thou me, and I shall be turned; for thou art the LORD my God. Surely after that I was turned, I repented; and after that I was instructed, I smote upon my thigh: I was ashamed, yea, even confounded, because I did bear the reproach of my youth.Jer 31:18