אבן העזר קע״וEven HaEzer 176

Se’if 1א׳

מִי שֶׁקִּדֵּשׁ אַחַת מִשְּׁתֵּי אֲחָיוֹת, וְאֵינוֹ יוֹדֵעַ אֵיזוֹ קִדֵּשׁ, אֲפִלּוּ לֹא הֻכְּרוּ מֵעוֹלָם, שֶׁלֹּא נִתְּנוּ לְבִיאָה, הֲווֹ קִדּוּשִׁין וְצָרִיךְ גֵּט לְכָל אַחַת וְאַחַת. מֵת, וְלוֹ אָח, חוֹלֵץ לִשְׁתֵּיהֶן. הָיוּ לוֹ שְׁנֵי אַחִים, אֶחָד חוֹלֵץ וְאֶחָד מְיַבֵּם לַשְּׁנִיָּה. קָדְמוּ שְׁנֵי הָאַחִים וְכָנְסוּ אֶת שְׁתֵּיהֶן, אֵין מוֹצִיאִים אוֹתָן מִיָּדָם. וְאִם נִמְלְכוּ בְּבֵית דִּין וְאָמְרוּ לָהֶם שֶׁיַּחֲלֹץ הָאֶחָד וִיְיַבֵּם הַשֵּׁנִי, וְהָלְכוּ שְׁנֵיהֶם וְיִבְּמוּ, יוֹצִיאוּ:

One who betrothed one of two sisters and doesn't know which he betrothed, even if they were never known, for they were not given [to him] for relations, it is betrothal and a get is required for each one of them. If he died and had a brother, the brother performs chalitzah for both of them. If he had two brothers, one performs chalitzah and one performs levirate marriage with the second. If the two brothers acted precipitously and brought them both into marriage, they do not remove them from them. But if they consulted with the beit din and they said to them that one should perform chalitzah and they other should perform levirate marriage, and both of them went and performed levirate marraige, they remove them.

Se’if 2ב׳

מִי שֶׁעָבַר וְיִבֵּם וַדַּאי אֲחוֹת זְקוּקָתוֹ, יוֹצִיא:

One who transgresses and performs a leverite marriage (Yibbum) with a connected sister, we remove them from the marriage.

Se’if 3ג׳

שְׁנַיִם שֶׁקִּדְּשׁוּ שְׁתֵּי אֲחָיוֹת, זֶה אֵינוֹ יוֹדֵעַ אֵיזוֹ קִדֵּשׁ וְזֶה אֵינוֹ יוֹדֵעַ אֵיזוֹ קִדֵּשׁ, וּמֵתוּ, לְזֶה אָח וּלְזֶה אָח, כָּל אֶחָד חוֹלֵץ לִשְׁתֵּיהֶן; וְאֵין שׁוּם אֶחָד מֵהֶם יָכוֹל לְיַבֵּם. לְזֶה אֶחָד וּלְזֶה שְׁנַיִם; הַיָּחִיד חוֹלֵץ לִשְׁתֵּיהֶן; וְהַשְּׁנַיִם, אֶחָד חוֹלֵץ לְאַחַת תְּחִלָּה, וְאַחַר כָּךְ יְיַבֵּם הַשֵּׁנִי לַשְּׁנִיָּה. וְאִם קָדְמוּ הַשְּׁנַיִם וְכָנְסוּ אַחַר שֶׁחָלַץ הַיָּחִיד, אֵין מוֹצִיאִים מִיָּדָם, אֲפִלּוּ שְׁנֵיהֶם כֹּהֲנִים. הָיוּ לְזֶה שְׁנֵי אַחִים וּלְזֶה שְׁנֵי אַחִים, אָחִיו שֶׁל זֶה חוֹלֵץ לְאַחַת, וְאָחִיו שֶׁל זֶה חוֹלֵץ לְאַחַת, וְאַחַר כָּךְ הָאָח הַשֵּׁנִי שֶׁל זֶה מְיַבֵּם חֲלוּצָתוֹ שֶׁל זֶה, וָאָח הַשֵּׁנִי שֶׁל זֶה מְיַבֵּם חֲלוּצָתוֹ שֶׁל זֶה. אִם קָדְמוּ שְׁנֵי הָאַחִים שֶׁל הָאֶחָד וְחָלְצוּ לִשְׁתֵּיהֶן, לֹא יְיַבְּמוּ הַשְּׁנֵי אַחִים הָאֲחֵרִים שֶׁל הַשֵּׁנִי לִשְׁתֵּיהֶן, אֶלָּא אֶחָד חוֹלֵץ וְאֶחָד מְיַבֵּם לַשְּׁנִיָּה. קָדְמוּ הַשְּׁנַיִם הָאַחֲרוֹנִים וְכָנְסוּ אַחַר שֶׁחָלְצוּ הַשְּׁנַיִם הָרִאשׁוֹנִים, אֵין מוֹצִיאִין מִיָּדָם:

Two men who married two sisters, and neither of them know which sister her married, and they die(the men), each of their brother performs the refusal ceremony for both of them and neither of them can do levirate marriage. If one of the men had one brother and the other, two, the one with one brother can do the refusal ceremony with both sisters and the one with two brothers, one of them can do the refusal ceremony with one sister first and then afterward, the second brother can do the levirate marriage. If the two brothers expedited the process and married the sisters after the one brother did the refusal ceremony, we don't divorce them from their hands, even if they are both priests. If both men had two brothers each, one of the brothers of one performs the refusal ceremony and the other brother performs the levirate marriage with aforementioned refused sister and the other second brother also performs the levirate marriage with the one his brother refused. If the two brothers expedited the process and performed the refusal service, the other two brothers cannot perform levirate marriage to the two women. Rather, one performs the refusal ceremony and one performs levirate marriage. If the two other brothers preceded and married the two women after the first two brothers performed the refusal ceremony, we do not remove them from their hands.