GOD'S WORD® Translation
When the day comes for the father to give his sons their inheritance, he can't treat the son of the wife he loves as if that son were the firstborn. This would show a total disregard for the real firstborn (the son of the wife he doesn't love).

American Standard Version
then it shall be, in the day that he causeth his sons to inherit that which he hath, that he may not make the son of the beloved the first-born before the son of the hated, who is the first-born:

Berean Study Bible
when that man assigns his inheritance to his sons he must not appoint the son of the beloved wife as the firstborn over the son of the unloved wife.

Douay-Rheims Bible
And he meaneth to divide his substance among his sons: he may not make the son of the beloved the firstborn, and prefer him before the son of the hated.

English Revised Version
then it shall be, in the day that he causeth his sons to inherit that which he hath, that he may not make the son of the beloved the firstborn before the son of the hated, which is the firstborn:

King James Bible
Then it shall be, when he maketh his sons to inherit that which he hath, that he may not make the son of the beloved firstborn before the son of the hated, which is indeed the firstborn:

World English Bible
then it shall be, in the day that he causes his sons to inherit that which he has, that he may not make the son of the beloved the firstborn before the son of the hated, who is the firstborn:

Young's Literal Translation
then it hath been, in the day of his causing his sons to inherit that which he hath, he is not able to declare first-born the son of the loved one, in the face of the son of the hated one -- the first-born.

Deuteronomy 21:16 Additional Translations ...