Reference for Yevamot 83:11

מתיב רב חנניה בכולן אני קורא בהן משום תקנת ערוה וכאן משום תקנת ולד ואם איתא כולהו משום תקנת ערוה

marrying his paternal sister,<span class="x" onmousemove="('comment',' A daughter of the first husband from another wife, believing her to be a stranger. ');">¹⁷</span> contracting levirate marriage with the wife of his maternal brother,<span class="x" onmousemove="('comment',' He, if his mother bore a son to her second husband, and that son died childless, would be contracting levirate marriage with his widow in the belief that he is the paternal brother while in fact he is his maternal brother whose wife is, therefore, forbidden to him under the penalty of kareth. ');">¹⁸</span>

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