What is the meaning of 'the Sun and the Moon' in Joseph's dream?

Joseph's prophecy is not flawed, the sun and moon did bow down to him. Rachel died in childbirth to Benjamin, it was not Leah, she died before they went to Egypt. Who was the moon?

Jacob

But who was the sun?

Israel

The reference to mother and father come from pagan religions of that time, that Jacob was exposed to.

When God created the sun and moon, he called them the Greater Light and the Lesser Light, as Jacob is referred to as the Lesser man, and Israel the Greater man.

On the types in the Old Testaments, the totality of God's redeemed people are typified in the Bible by the heavenly luminaries, the three lights created by God—the sun, the moon, and the stars (Gen. 1:14-18).

They are used to signify the whole house of Jacob, which was chosen and redeemed by God (37:9-10). God chose and redeemed them not according to what they were and did in their natural life but according to the will of God's sovereignty and His abundant mercy (Rom. 9:10-18). According to man’s view, they were evil and defiled, but according to God’s view, they were as bright as the heavenly luminaries, the three lights. Among them Jacob was like the sun, his wife Rachel was like the moon, and his twelve sons were like twelve stars.

The New Testament uses the sun, the moon, and the stars to signify the totality of the believers in the Old and New Testaments with the sign of the universal corporate woman (Rev. 12:1). Both the Old Testament and the New Testament believers are the saints chosen and redeemed by God. God looks at them according to His eternal view and the purpose of His economy, not according to what they are and do. In this view, they are clean and bright, like the God-created heavenly luminaries, the three lights, which serve as symbols of them.

The universal woman in Revelation 12:1 is clothed with the sun. The sun signifies God's people in the New Testament age. Before Christ came to the world, the Old Testament age was like a dark night. When Christ, as the rising sun, came from on high (Luke 1:78), the age of the sun came. Since Christ has come, the New Testament believers are living in the day, and since they are a part of Christ, they are part of the sun. The church, which is composed of all the New Testament believers, shines corporately in the day to show forth the glory of God (Phil. 2:15-16). The woman, who is clothed with the sun, indicates also that the New Testament believers constitute the major part of God’s people.

Before Christ came, it was the age of the moon, which signifies God's people in the Old Testament age. The moon is underneath the feet of the universal woman because the age of the moon is the age of the law, which, in God’s eyes, should not be exalted like the stars.

The stars signify the patriarchs, God's people before the law was given, shining individually in the dark night with the divine, heavenly light. According to Daniel 12:3, God’s redeemed in the Old Testament, that is, those who turn many to righteousness, who lead people to God, and who do righteousness by God, will shine as stars forever and ever.

In the New Testament, the believers who have received God's grace in the New Testament should shine much more as the heavenly stars in today’s dark age. The apostle Paul solemnly charges in Philippians 2:15-16 that we should be children of God without blemish in the midst of a crooked and perverted generation, among whom we shine as luminaries, reflecting the word of life, the embodiment of Christ. The Lord Jesus also said that we are the light of the world, and He charged us to let our light shine over people (Matt. 5:14-16).

The story of Joseph's dream is central in the whole scheme of events. It is obvious that the mention of the dream is indicative of the surety of its later fulfillment. The moon in the dream must be a parent of Joseph, and since his mother was not in the picture, that person would be someone Joseph considered a parent. That was the person who bought him from Egypt, adopted him, and later taught him dream interpretation.

The Sun and the Moon do definitely represent his father and mother:

Genesis 37:10 NKJV So he told it to his father and his brothers; and his father rebuked him and said to him, "What is this dream that you have dreamed? Shall your mother and I and your brothers indeed come to bow down to the earth before you?"

The bowing down does not refer to the physical act of bowing; what it refers to is his having a position superior to them.

Which actually happened and not only did he hold a superior position, but he became their provider and benefactor. And even though he had much power over their lives he still acquiesced to his father with his sons.

Genesis 48:11through 14 NKJV And Israel said to Joseph, "I had not thought to see your face; but in fact, God has also shown me your offspring!" 12 So Joseph brought them from beside his knees, and he bowed down with his face to the earth. 13 And Joseph took them both, Ephraim with his right hand toward Israel's left hand, and Manasseh with his left hand toward Israel's right hand, and brought them near him. 14 Then Israel stretched out his right hand and laid it on Ephraim's head, who was the younger, and his left hand on Manasseh's head, guiding his hands knowingly, for Manasseh was the firstborn.

and

Genesis 48:17 through 19 NKJV Now when Joseph saw that his father laid his right hand on the head of Ephraim, it displeased him; so he took hold of his father's hand to remove it from Ephraim's head to Manasseh's head. 18 And Joseph said to his father, "Not so, my father, for this one is the firstborn; put your right hand on his head." 19 But his father refused and said, "I know, my son, I know. He also shall become a people, and he also shall be great; but truly his younger brother shall be greater than he, and his descendants shall become a multitude of nations.

Even though Joseph's dream was predictive of events to come, it in no way degraded the positions of Joseph's parents. It was not God's intent to change the family hierarchy, but to save the Hebrew Nation for his future purposes.

Hope this helps.