Genesis 35:22
And it came to pass, when Israel dwelled in that land, that Reuben went and lay with Bilhah his father's concubine: and Israel heard it. Now the sons of Jacob were twelve:
Torrey's Topical Textbook—AKJV

Genesis 49:28
All these are the twelve tribes of Israel: and this is it that their father spoke to them, and blessed them; every one according to his blessing he blessed them.
Torrey's Topical Textbook—AKJV