In general, birth order in the Bible reflects the progression of spiritual states, but the specifics of those states depends greatly on context: who the people in question are, and whether we’re talking about spiritual states as they flow to us from the Lord, or spiritual states as we advance through them to approach the Lord. For example, Esau was older than Jacob (by minutes, but it mattered), and as the elder represents a more internal spiritual state: the desire for good, and the ideas that flow from that desire. Jacob represents a more external state: the understanding of ideas that lead to good. The switched blessing, with Jacob getting the blessing Isaac meant for Esau, shows that to progress in life we need to put our understanding first for a while, though ultimately our loves will catch up and ultimately determine our true character. A similar thing happens when Jacob crosses his hands to give Ephraim, the younger of Joseph’s sons, the primary blessing over his older brother Manasseh. Both those cases describe blessings coming from the Lord, with the highest states coming from Him and extending down through lower states to get to us. There is a sort of opposite dynamic in the story of Leah and Rachel. There Jacob (representing the Lord himself, as a human, in His childhood) is advancing from more external states to more internal ones. In this case, then, the older daughter, Leah, represents a more external state which He had to work through to reach the more internal state represented by Rachael.