'Twelve' in the Bible

Twelve years they had served Chedorlaomer [the most powerful king in the invading confederacy], but in the thirteenth year they rebelled.

As for Ishmael, I have heard and listened to you; behold, I will bless him, and will make him fruitful and will greatly multiply him [through his descendants]. He will be the father of twelve princes (chieftains, sheiks), and I will make him a great nation.

These are the sons of Ishmael and these are their names, by their settlements, and by their encampments (sheepfolds); twelve princes (sheiks) according to their tribes.

While Israel was living in that land, Reuben [his eldest son] went and lay with Bilhah his father’s concubine, and Israel heard about it.Now Jacob had twelve sons—

But they said, “Your servants are twelve brothers [in all], the sons of one man in the land of Canaan; please listen: the youngest is with our father today, and one is no longer alive.”

We are twelve brothers, sons of our father; one is no longer alive, and the youngest is with our father today in the land of Canaan.’

All these are the [beginnings of the] twelve tribes of Israel, and this is what their father said to them as he blessed them, blessing each one according to the blessing appropriate to him.