Why is the birth of twins a Chidush for Rivka?

Question

Background:
In Parshat Toldot, Rivka conceives and is troubled by the discomfort.
She goes to ask Hashem and it is explained to her that 2 nations are struggling within her, so she already knows that she is birth multiples.
But in pasuk 24, the text reads, " וְהִנֵּה תוֹמִם בְּבִטְנָהּ" "and behold, there were twins in her womb" (text and translation God via Chabad, bold, mine).

Question:
If she knew that there was more than one child, why was it a surprise that 2 were born?
The Rashbam says that the use of "hineh" is reserved for a "chidush" -- something that was not known before, and he gives 2 examples.
How was this a surprise?

The Sforno says that before they were born, it was known that there were 2 babies.
Was she expecting one baby to kill the other in the womb?

My first thought was that the prophecy regarding 2 nations was metaphorical -- that a single child would struggle with his nature so the birth of two separate babies was unexpected.
But if that were the case, why would pasuk 22 state, "וַיִּתְרֹצֲצוּ הַבָּנִים בְּקִרְבָּהּ" and say explicitly that there was more than one child in there (and why would the Sforno endorse the idea that this was known)?
Is it that the pasuk tells us but she doesn't know?
If so, why tell us at all if the text is going to use the language of "behold"?

Answer 1

The העמק דבר says that the wonder is that they were so different. She thought they would be more similar, but it turned out surprising that they were twins in the same womb, given how different they were.

He is putting the emphasis on the whole phrase of "twins in her womb". He also finds significance in that the word for twins is written without the alef, showing they were lacking the typical twin similarity.

The Lubavitcher Rebbe explains (Likkutei Sichos Vol. 30 p. 111ff) that according to Rashi, the purpose of the phrase is to explain why she had a full 9 month pregnancy instead of a 7 month one - the word for twins is written without an alef to show that since one was a Rasha, Rivkah did not merit to have a shorter pregnancy (which would have shortened the unusual pain she was experiencing). Thus the behold doesn't necessarily imply something previously completely unknown.

Answer 2

Rav Hirsch says that the fact that they were going to be "two nations" and were completely different nations implied that they were non-identical twins. However he states that the word used implies identical (complete) twins.

The surprising thing was that they were really identical twins. The only difference was in their constitution, that the one - as we are immediately told - was much more developed, stronger, than the other. Perhaps also the way the word is spelled חםר דחסר: תומם for תאומים (as in Shmos 26:24) points to the exterior complete similarity. This complete exterior similarity taken together with the complete dissimilarity which had been predicted would develop in the future, could well have been designed to draw attention to the fact that the germ of this future dissimilarity lay deep below the surface, and so be the means of bringing about that this deep inner difference in the two boys be specially studied quite early.

Also see the commentary on "Vayigdelu Hanearim" which explains that the difference between them did not become apparent until after Avraham died (when they were 15).

Answer 3

Darosh Darosh Moshe page 73 says that the surprise was that it was immediately noticeable that Yaakov was a Ish Tam and that Eisav was not.

Answer 4

The Chumash HaEmek Dovor deals with the question.

The Beis Hamedrash of Shem told her (v 23) that

שְׁנֵי גוֹיִם בְּבִטְנֵךְ וּשְׁנֵי לְאֻמִּים מִמֵּעַיִךְ יִפָּרֵדוּ

Two nations are in your womb, and two kingdoms will separate from your innards..

which she understood to mean that the difference between them would be evident immediately when they emerged from the womb.

V 24 tells us that

וְהִנֵּה תוֹמִם בְּבִטְנָהּ

there were twins in her womb.

that is “תוֹמִם" and not “תְאוּמִים".

The Haemek Dovor understands that she thought that the difference between the twins would be seen when they emerged from the womb (as she had been told)

and the surprise was that even in the womb they were already תוֹמִם without an א to teach us that they were already different.