Reference for Yevamot 200:1

היו לו אחים מן הראשון ואחים מן השני שלא מאותה האם הוא חולץ ומייבם והם אחד חולץ ואחד מייבם

IF HE<span class="x" onmousemove="('comment',' The son whose father is unknown. ');">¹</span> HAD BROTHERS BY THE FIRST<span class="x" onmousemove="('comment',' Husband of his mother. ');">²</span> AND ALSO BROTHERS BY THE SECOND,<span class="x" onmousemove="('comment',' Husband of his mother. ');">²</span> BUT NOT BY THE SAME MOTHER, HE<span class="x" onmousemove="('comment',' The son whose father is unknown. ');">¹</span>

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