Deuteronomy 25:10

And his name shall be called in Israel "The house of him that hath his shoe loosed. " So the disgrace would rest upon the man, even in the nickname which he bore, for having neglected the duty of relationship to his brother. There is no discrepancy between this passage and the law of Leviticus 18. For the marriage with one's sister-in-law was forbidden when there were children, since the integrity of the brother's house was thus upheld; here it was commanded in order to keep the family of the brother from becoming extinct.