The term 'TWIN IN GENESIS' refers to the biblical story of Jacob and Esau, who were twin brothers born to Isaac and Rebekah in the book of Genesis. The crossword solution for this term is 'Esau, ' which is a four-letter word. Esau was the older brother of Jacob and was known for his hunting skills. He sold his birthright to Jacob for a bowl of stew, and later reconciled with him after a long separation.