1 Samuel 17:14

And David is the youngest, and the three eldest have gone after Saul,

1 Samuel 16:11

And Samuel saith unto Jesse, 'Are the young men finished?' and he saith, 'Yet hath been left the youngest; and lo, he delighteth himself among the flock;' and Samuel saith unto Jesse, 'Send and take him, for we do not turn round till his coming in hither.'

Genesis 25:23

And Jehovah saith to her, 'Two nations are in thy womb, and two peoples from thy bowels are parted; and the one people than the other people is stronger; and the elder doth serve the younger.'

Treasury of Scripture Knowledge

Summary

And David was the youngest: and the three eldest followed Saul.

Bible References

The youngest

1 Samuel 16:11
And Samuel saith unto Jesse, 'Are the young men finished?' and he saith, 'Yet hath been left the youngest; and lo, he delighteth himself among the flock;' and Samuel saith unto Jesse, 'Send and take him, for we do not turn round till his coming in hither.'
Genesis 25:23
And Jehovah saith to her, 'Two nations are in thy womb, and two peoples from thy bowels are parted; and the one people than the other people is stronger; and the elder doth serve the younger.'