And a woman unto another thou dost not take, to be an adversary, to uncover her nakedness beside her, in her life. [Leviticus 18:18 YLT]
Neither shalt thou take a wife to her sister, to vex her, to uncover her nakedness, beside the other in her life time. [Leviticus 18:18 KJV]
In reading of Jacob's marriages and his marrying the daughters of Laban (who may have had different mothers ?) I referenced Leviticus 18:18 and discovered that Robert Young does not state 'sister' but 'adversary'.
As far as I can understand, Young seems to be rendering אֲחֹתָ֖הּ as 'another' rather than 'sister'.
On the face of it, Young appears to be stating that a man must not take any woman to be a rival in any way to another wife, but to wait for the decease of the one before marrying the second.
Thus the text, in Robert Young's hands, would appear to be all about matrimonial peacefulness (and freedom from strife) and there would seem to be, in Robert Young's hands, no prohibition to Jacob to marry Leah and Rachel, being sisters.
I am looking for comment on the original Hebrew, please.