And even though Judah became the strongest of his brothers and King David eventually came from that family, the firstborn rights stayed with Joseph. 1 Chronicles 5:2 (MSG)
To this point in the book, the author of Chronicles has focused his genealogical listings on the tribe of Judah and particularly the house of David. We see it yet again in the verse above as the writer appears to explain to his readers why first born rights among the tribes of Israel were not with the first born Reuben, nor with his favorite team: Judah. He does, however, bring up an interesting connection.
Joseph and David were both the youngest among their brothers and were derided as such. God raised both of them to prominence over their brothers and gave them both positions of power, authority, and blessing. Both David and Joseph are constant reminders that God is a God of the underdog. God raises the lowest, most humble. When we are at our weakest, God tends to performs His greatest works in our lives.