Your Brother, The Son of Your Mother

This may be obvious, but I wanted to speak it out nonetheless. I was learning through a recent daf {Kiddushin 80b} in the daf Yomi cycle and came across this:

From where do we know these words? Rabbi Yochanan said in the name of Rabbi Yishmael: A hint to {the prohibition on} seclusion from the Torah, from where? For it is stated {Devarim 13:7}:

ז כִּי יְסִיתְךָ אָחִיךָ בֶן-אִמֶּךָ אוֹ-בִנְךָ אוֹ-בִתְּךָ אוֹ אֵשֶׁת חֵיקֶךָ, אוֹ רֵעֲךָ אֲשֶׁר כְּנַפְשְׁךָ--בַּסֵּתֶר לֵאמֹר: נֵלְכָה, וְנַעַבְדָה אֱלֹהִים אֲחֵרִים, אֲשֶׁר לֹא יָדַעְתָּ, אַתָּה וַאֲבֹתֶיךָ.

7 If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, that is as thine own soul, entice thee secretly, saying: 'Let us go and serve other gods,' which thou hast not known, thou, nor thy fathers;

{Where "your brother the son of your mother" is understood as a single phrase.}
Now does the son of a mother entice, while the son of a father not entice? Rather to say to you that a son may seclude himself with his mother, but is forbidden to seclude himself with all of the forbidden relations in the Torah.

The gemara continues with trying to figure out the pashteih dikra, and cites Abaye that it means "your mother's son," and all the more so your father's son. So the simple text only refers to a single son.

And my immediate thought was how this is based on how the phrase כִּי יְסִיתְךָ אָחִיךָ בֶן-אִמֶּךָ is taken as a single phrase, such that it is your brother who is the son of your mother; but that we can easily take it as achicha, which would be a "typical" brother, who is a paternal {and possibly simultaneously maternal} brother, and separately, the son of your mother, that is a maternal brother.

Then I looked in Rashi on the pasuk, in Reeh, and found that this is exactly how Rashi interprets it:

your brother from the father[’s side].
the son of your mother from the mother[’s side].

I am not entirely sure how Ibn Ezra understands it. He writes:

יג, ז]
כי יסיתך אחיך -
הטעם אפילו אחיך.

וטעם בן אמך
שהייתם בבטן אחת והאם כגוף והאב כצורה והצורה לא יבינוה, כי אם מתי מעט.

Is he treating brother as one, and son of mother as a separate entity, as an intensifying case of the emotion and connection one would feel to him? It certainly seems that way to me. Or alternatively, is he offering explanation of why the pasuk elaborates, and it is speaking of a single brother, who is both a maternal and paternal brother. I can certainly see it this way as well.

Aharon ben Yosef the Karaite takes it as a single entity, of one who is exclusively the son of the mother and not the son of the father. (At least as I understand him.) He references Tehillim 50:

כ תֵּשֵׁב, בְּאָחִיךָ תְדַבֵּר; בְּבֶן-אִמְּךָ, תִּתֶּן-דֹּפִי.

20 Thou sittest and speakest against thy brother; thou slanderest thine own mother's son.

This raises an interesting question about Biblical parallelism. Is it mere echoing in other language, or is it an intensification? This is something of a discussion even among modern Biblical scholars. But here, is the achicha the same as ben imecha?

Rashi in Tehillim makes no overt distinction between the two (such that it could be either), but explains why "your own mother's son" should be a reason why it is worse:

your mother’s son with whom you have no [legal] quarrel, since he does not inherit with you.

and indeed, that is a reason Aharon ben Yosef offers for their special closeness.

I would read Onkelos as having them a single individual, as there is not elaboration in:

אֲרֵי יִמְלְכִנָּךְ אֲחוּךְ בַּר אִמָּךְ אוֹ בְּרָךְ אוֹ בְּרַתָּךְ אוֹ אִתַּת קְיָמָךְ, אוֹ חַבְרָךְ דִּכְנַפְשָׁךְ--בְּסִתְרָא לְמֵימַר: נְהָךְ, וְנִפְלַח לְטָעֲוָת עַמְמַיָּא, דְּלָא יְדַעְתָּא, אַתְּ וַאֲבָהָתָךְ.

Tg Yerushalmi has the same non-elaboration. Targum Yonatan makes it overt as "your brother the son of your mother, and all the more so the son of your father" making it clear that the Biblical text only was explicitly talking about one person, the maternal brother. This is then echoing Abaye in our gemara in Kiddushin.

Can the trup help us choose? Not really, since it is after all just going to select one of two possible perushim, and so is a commentary in its own right. But the trup is:

כִּ֣י יְסִֽיתְךָ֡ אָחִ֣יךָ בֶן־אִ֠מֶּךָ אֽוֹ־בִנְךָ֨ אֽוֹ־בִתְּךָ֜ א֣וֹ ׀ אֵ֣שֶׁת חֵיקֶ֗ךָ א֧וֹ רֵֽעֲךָ֛ אֲשֶׁ֥ר כְּנַפְשְׁךָ֖ בַּסֵּ֣תֶר לֵאמֹ֑ר נֵֽלְכָ֗ה וְנַֽעַבְדָה֙ אֱלֹהִ֣ים אֲחֵרִ֔ים אֲשֶׁר֙ לֹ֣א יָדַ֔עְתָּ אַתָּ֖ה וַֽאֲבֹתֶֽיךָ

In terms of parsing this, there is a pazer on כִּ֣י יְסִֽיתְךָ֡ and a telisha gedolah on בֶן־אִ֠מֶּךָ. Both are on equal footing breaking off the clause, so the earlier one in the pasuk functions first. So first the pazer breaks off, and then the telisha gedolah. There is a munach on achicha, such that it all is one phrase. But does that really show anything? Not that I know of, since these are the lowest of disjunctive accents, meaning that there are no other disjunctive accents to subdivide it, such that the munach had to come there. And in o vincha o vitecha there is no disjunctive accent in between anyway.

However, perhaps we can make a big deal over the lack of the word או in between achicha and ven imecha. The word או stands between every other scenario in the verse, so its absence here may indeed be significant.

What happens in the general case of lists in Tanach, particularly long lists? Some prime examples:
וַיֹּאמֶר יְהוָה אֵלָיו, מִי שָׂם פֶּה לָאָדָם, אוֹ מִי-יָשׂוּם אִלֵּם, אוֹ חֵרֵשׁ אוֹ פִקֵּחַ אוֹ עִוֵּר--הֲלֹא אָנֹכִי, יְהוָה
כִּי-תֵצֵא אֵשׁ וּמָצְאָה קֹצִים, וְנֶאֱכַל גָּדִישׁ, אוֹ הַקָּמָה, אוֹ הַשָּׂדֶה--שַׁלֵּם יְשַׁלֵּם, הַמַּבְעִר אֶת-הַבְּעֵרָה.
כִּי-יִתֵּן אִישׁ אֶל-רֵעֵהוּ חֲמוֹר אוֹ-שׁוֹר אוֹ-שֶׂה, וְכָל-בְּהֵמָה--לִשְׁמֹר; וּמֵת אוֹ-נִשְׁבַּר אוֹ-נִשְׁבָּה, אֵין רֹאֶה.
אוֹ נֶפֶשׁ, אֲשֶׁר תִּגַּע בְּכָל-דָּבָר טָמֵא, אוֹ בְנִבְלַת חַיָּה טְמֵאָה אוֹ בְּנִבְלַת בְּהֵמָה טְמֵאָה, אוֹ בְּנִבְלַת שֶׁרֶץ טָמֵא; וְנֶעְלַם מִמֶּנּוּ, וְהוּא טָמֵא וְאָשֵׁם.
נֶפֶשׁ כִּי תֶחֱטָא, וּמָעֲלָה מַעַל בַּיהוָה; וְכִחֵשׁ בַּעֲמִיתוֹ בְּפִקָּדוֹן, אוֹ-בִתְשׂוּמֶת יָד אוֹ בְגָזֵל, אוֹ, עָשַׁק אֶת-עֲמִיתוֹ.
וְהָיָה, כִּי-יֶחֱטָא וְאָשֵׁם--וְהֵשִׁיב אֶת-הַגְּזֵלָה אֲשֶׁר גָּזָל אוֹ אֶת-הָעֹשֶׁק אֲשֶׁר עָשָׁק, אוֹ אֶת-הַפִּקָּדוֹן אֲשֶׁר הָפְקַד אִתּוֹ; אוֹ אֶת-הָאֲבֵדָה, אֲשֶׁר מָצָא.
וְכֹל אֲשֶׁר-יִפֹּל-עָלָיו מֵהֶם בְּמֹתָם יִטְמָא, מִכָּל-כְּלִי-עֵץ אוֹ בֶגֶד אוֹ-עוֹר אוֹ שָׂק, כָּל-כְּלִי, אֲשֶׁר-יֵעָשֶׂה מְלָאכָה בָּהֶם; בַּמַּיִם יוּבָא וְטָמֵא עַד-הָעֶרֶב, וְטָהֵר.
אָדָם, כִּי-יִהְיֶה בְעוֹר-בְּשָׂרוֹ שְׂאֵת אוֹ-סַפַּחַת אוֹ בַהֶרֶת, וְהָיָה בְעוֹר-בְּשָׂרוֹ, לְנֶגַע צָרָעַת--וְהוּבָא אֶל-אַהֲרֹן הַכֹּהֵן, אוֹ אֶל-אַחַד מִבָּנָיו הַכֹּהֲנִים.
וְאִם-תֵּרָאֶה עוֹד בַּבֶּגֶד אוֹ-בַשְּׁתִי אוֹ-בָעֵרֶב, אוֹ בְכָל-כְּלִי-עוֹר--פֹּרַחַת, הִוא: בָּאֵשׁ תִּשְׂרְפֶנּוּ, אֵת אֲשֶׁר-בּוֹ הַנָּגַע.

A particularly relevant example, IMHO, in Vayikra 18:9:
עֶרְוַת אֲחוֹתְךָ בַת-אָבִיךָ, אוֹ בַת-אִמֶּךָ, מוֹלֶדֶת בַּיִת, אוֹ מוֹלֶדֶת חוּץ--לֹא תְגַלֶּה, עֶרְוָתָן.
such that achotecha is explained as being either one or the other, and there is a notable absence of או in between.
And then in Vayikra 20:
וְאִישׁ אֲשֶׁר-יִקַּח אֶת-אֲחֹתוֹ בַּת-אָבִיו אוֹ בַת-אִמּוֹ וְרָאָה אֶת-עֶרְוָתָהּ וְהִיא-תִרְאֶה אֶת-עֶרְוָתוֹ, חֶסֶד הוּא--וְנִכְרְתוּ, לְעֵינֵי בְּנֵי עַמָּם; עֶרְוַת אֲחֹתוֹ גִּלָּה, עֲו‍ֹנוֹ יִשָּׂא.
And we also have:
אָרוּר, שֹׁכֵב עִם-אֲחֹתוֹ--בַּת-אָבִיו, אוֹ בַת-אִמּוֹ; וְאָמַר כָּל-הָעָם, אָמֵן.

In terms of vav connecting, we can omit it in a list until the last element:
רְאוּבֵן שִׁמְעוֹן, לֵוִי וִיהוּדָה.

So I think just the absence of או is sufficient in this case to establish it like the gemara, and not like Rashi (and whatever midrashic source he relied upon, if he did).