Cross reference
Genesis 38:4
4 She conceived again, and bore a son; and she named him Onan.
Genesis 46:12
12 The sons of Judah: Er, Onan, Shelah, Perez, and Zerah; but Er and Onan died in the land of Canaan. The sons of Perez were Hezron and Hamul.
Numbers 26:19
19 The sons of Judah: Er and Onan; and Er and Onan died in the land of Canaan.