The Dodecagamist

Yeshaya 4:1:

א וְהֶחֱזִיקוּ שֶׁבַע נָשִׁים בְּאִישׁ אֶחָד, בַּיּוֹם הַהוּא לֵאמֹר, לַחְמֵנוּ נֹאכֵל, וְשִׂמְלָתֵנוּ נִלְבָּשׁ: רַק, יִקָּרֵא שִׁמְךָ עָלֵינוּ--אֱסֹף, חֶרְפָּתֵנוּ

1 And seven women shall take hold of one man in that day, saying: 'We will eat our own bread, and wear our own apparel; only let us be called by thy name; take thou away our reproach.'

I'd like to share one of my favorite Yerushalmis. It occurs in Yerushalmi Yevamot 28b, the fourth perek, halacha 12.

The Mishna:

דף כח, ב פרק ד הלכה יב משנה

ארבעה אחין נשואין לארבעה נשים ומתו
אם רצה הגדול שבהם מייבם את כולן הרשות בידו
היה נשוי לשתי נשים ומת
ביאתה או חליצתה של אחת מהן פוטרת צרתה
היתה אחת כשירה ואחת פסולה
אם היה חולץ חולץ לפסולה
ואם היה מייבם מייבם לכשירה

Four brothers are married to four women {who are not related to each other}, and they {the men} die.
If the eldest of them {of the remaining brothers - not the four brothers who died} wishes to perform levirate marriage on all of them {the four widows}, he is permitted to do so.

{However,} if one man was married to two women and he died,
The performance of levirate marriage or chalitza upon one of them exempts her fellow wife {such that he need not, and may not, perform levirate marriage or chalitza on the other widow}.

If one of them {the two widows} was fit {to marry a Kohen} and one was unfit,
If he performs chalitza {to allow the widow to marry anyone else}, he should perform chalitza on the unfit.
{The reason for this is that just as divorce renders a woman "unfit" to marry a Kohen, so does the act of chalitza. If he would perform chalitza on the "fit" widow, she would then be unable to marry a Kohen if she so desired. There is no reason to do this chalitza and harm her in this way. Rather, he should perform chalitza on the widow who was unfit already, for other reasons, to marry a Kohen, since the chalitza will not harm her. Then, based on the rule laid down earlier in the Mishna, the co-widow is also free to marry anyone else, now including a Kohen.}

If he chooses to perform levirate marriage, he may perform levirate marriage with the "fit" one.
{That is, if he wishes to marry the "unfit" one he may, and if he wishes to marry the "fit" one he may. The idea is that since he is marrying her, he may marry whichever one he wants to marry. This differs from the preceding case because in the preceding case he was not going to marry either of them anyway, so we choose the scenario that lacks the damage to either of them.}

The Gemara:

דף כח, ב פרק ד הלכה יב גמרא
ארבעה אחין כו'
דלמא תלת עשר אחין הויין ומתין תרין עשר דלא בנין
אתיון בעיון מתייבמה קומי רבי
אמר ליה רבי איזיל ייבם
אמר ליה לית בחיילי.
והם אומרות כל חדא וחדא אנא מזייננא ירחי.
אמר ומאן זיין ההוא ירחא דעיבורא?
אמר רבי אנא זייננא ירחא דעיבורא
וצלי עליהון ואזלון להון
בתר תלת שנין אתון טעינין תלתין ושיתא מיינוקין אתון וקמנו להן קומי דרתה דרבי.
סלקין ואמרין ליה לרע קרייא דמיינוקין בעיין מישאל בשלמא.
אודיק ר' מן כוותא וחמתון.
אמר לון מה עיסקיכון.
אמרין ליה אנן בעיין תיתין לן ההוא ירחא דעיבורא.
ויהיב להון ההוא ירחא דעיבורא

"Four brothers, etc."

There was an incident in which there were thirteen brothers, and twelve of them died without sons.
They {the twelve widows} came and declared their wish to undergo levirate marriage, before Rabbi.
Rabbi said to him {the surviving brother} go and perform levirate marriage.
He said to him {Rabbi}: I do not have the means {to support such a large family}.
And each one of them {the widows} said: I am prepared to provide support for my month. {and, since there were twelve widows, all 12 months of the year are covered.}
He {the surviving brother} said: And what about the extra month of the leap year?
{That is, in the Hebrew calendar, seven times every nineteen years is a leap year, in which there is an extra month of Adar added, for a total of 13 months. Even if each of the twelve widows takes on one month of the year, in a leap year there will be an uncovered month, and the surviving brother did not wish to accept the responsibility of providing for such a large family during that month.}
Rabbi said: I will provide for the leap month.
And he prayed for them {to succeed} and they went off to themselves.
After three years, they came carrying 36 infants. They came stood before the residence of Rabbi.
His attendants went out and said to him: below is a village of infants coming to greet you.
Rabbi looked from the window and saw them.
He said to them: What is your business?
They said to him: We desire that you give us sustenance for this leap month.
And he gave them sustenance for that lape month.

The gemara continues with the story (and derivation of the story) of someone who also had many descendants, Oved Edom, and then with the derivation of the law mentioned in the Mishna that chalitza on one widow exempts other widows from that same marriage, and how the same goes for yibbum. I won't translate in this post, but here it is:

כתיב (שמואל ב ו) וישב ארון יי עם עובד אדום בביתו שלשה חדשים ויברך יי וגו' במה בירכו בבנים. הדא הוא דכתיב (דברי הימים א כו) כל אלה מבני עובד אדום המה ובניהם ואחיהם איש חיל בכח לעבודה ששים וגו'. דהוות כל חדא מינהן ילדה תריי בכל ירחא. הא כיצד טמאה שבעה. וטהרה ז' וילדת. טמאה ז' וטהרה ז' וילדת שית עשר לכל ירח לתלתא ירחין הא ארבעין ותמניי' והוא אשתין הא חמשין וארבעה

דף כט, א פרק ד הלכה יב גמרא ותמנותיהון הא אשתין ותריי. הדא היא דכתיב ששים ושנים לעובד אדום א"ר בא בר זבדא כתיב (דברים כה) ונקרא שמו בישראל בית חלוץ הנעל. בית שהוא ניתר בחליצה אחת. אף בביאה כן. חליצה פוטר וביאה פוטר. כמה דאת אמר בחליצה. כן את אמר בביאה.

Finally, the gemara asks a question relevant to the aforementioned case of the yibbum involving 12 widows. The following is my own interpretation of the conclusion of the gemara:

ומהו להערים?
וכי רבי טרפון אביהן של כל ישראל לא הערים?
קידש שלש מאות נשים בימי רעבון על מנת להאכילן בתרומה!
תמן אין כל אחת ואחת ראויה לוכל בתרומה.
ברם הכא כל אחד ואחד ראוי לייבם

May they resort to trickery?
{That is, he did not want to support all these wives, as well as children that might result -- and we see there were many. The brother + 12 wives + 36 children = 49 people. Could they have made a sham marriage, to create a family unit, in which they were halachically married, but not really intend to really consummate? This would presumably be the Rabbinic yibbum betrothal called maamar, but alternatively would be not having all those children. The gemara will suggest why this should be possible.}
Did not Rabbi Tarfon, the father of all of Israel, not resort to such trickery?
He betrothed 300 women during a famine in order to feed them teruma!
{Only Kohanim and members of a Kohen's household may eat teruma. On a Biblical level, a woman betrothed to a Kohen may eat teruma. Since Rabbi Tarfon was a Kohen, he made a sham marriage to all these women so that they could eat teruma during the time of famine. The gemara will explain why this case is different.}
There, without this, none of those women were allowed to eat teruma.
However, here, each of them {the 12 widows} were fit {and waiting} to do yibbum {and thus there was an obligation to either do real yibbum or else do chalitza.}