Genesis 37:3 New English Translation

³Now Israel loved Joseph more than all his sons^[a] because he was a son born to him late in life,^[b] and he made a special^[c] tunic for him.

Genesis 37:3 tn The disjunctive clause provides supplemental information vital to the story. It explains in part the brothers’ animosity toward Joseph.sn The statement Israel loved Joseph more than all his sons brings forward a motif that played an important role in the family of Isaac—parental favoritism. Jacob surely knew what that had done to him and his brother Esau, and to his own family. But now he showers affection on Rachel’s son Joseph.
Genesis 37:3 tn Heb “a son of old age was he to him.” This expression means “a son born to him when he [i.e., Jacob] was old.”
Genesis 37:3 tn It is not clear what this tunic was like, because the meaning of the Hebrew word that describes it is uncertain. The idea that it was a coat of many colors comes from the Greek translation of the OT. An examination of cognate terms in Semitic suggests it was either a coat or tunic with long sleeves (cf. NEB, NRSV), or a tunic that was richly embroidered (cf. NIV). It set Joseph apart as the favored one.

New English Translation (NET)