Although they didn't 'team up' through marriage, there are quite a few sources that do point to an association with them in religious practises etc.
Yalkut Shimoni, Bereishis 80 - Avraham sent for Shem to perform bris milah for him and Yishmael:
רבן גמליאל אומר שלח אברהם וקרא לשם בן נח ומל את בשר ערלתו וישמעאל בנו
Rabban Gamliel said, Avraham sent and called for Shem the son of Noach, and he (Shem) circumcised the flesh of his (Avraham's) foreskin and Yishmael his son.
Targum Yonason Bereishis 22:19 - After the Akeidah, malachim took Yitzchak and brought him to the yeshiva of Shem where he stayed for three years:
וּדְבָרוּ מַלְאֲכֵי מְרוֹמָא יַת יִצְחָק וְאוֹבִלוֹהִי לְבֵי מֶדְרָשָׁא דְשֵׁם רַבָּא וַהֲוָה תַּמָן תְּלַת שְׁנִין
And the angels upon high took Yitzchak and brought him into the beis medrash (house of learning) of Shem the Great; and he was there three years.
Alternatively, see Bereishis Rabbah 56:11 where the Midrash says on the same pasuk (22:19) that Avraham sent him to learn Torah from Shem, the reason being because - "Avraham said: ‘All that has happened to me is only because I engaged in Torah and mitzvos; so I do not want it to ever depart from my descendants.’"
Whilst you mention that Yaakov learnt by Shem and Ever for 14 years, a period that followed his flight from Esav (as mentioned in Rashi 28:11 here) there are sources that point to the fact that he already enjoyed an association with them...
When it mentions in Bereishis 25:27 that as Yaakov grew up, he was:
אִ֣ישׁ תָּ֔ם יֹשֵׁ֖ב אֹהָלִֽים׃ - And Yaakov was a simple man who dwelt in tents.
It writes in Bereishis Rabbah 63:10 that these "tents" were a reference to him learning by Shem and Ever:
וְיַעֲקֹב אִישׁ תָּם ישֵׁב אֹהָלִים, שְׁנֵי אֹהָלִים, בֵּית מִדְרָשׁוֹ שֶׁל שֵׁם וּבֵית מִדְרָשׁוֹ שֶׁל עֵבֶר
"And Yaakov was a simple man who dwelt in tents" - These were two tents; the house of learning of Shem and the house of learning of Ever.
And this wasn't the odd appearance every now and again, it was a constant to and fro. It writes in the Midrash Tanchuma (Buber edition), Vayishlach 9 that his level of ameilus (toil) was so great that he would flit from Shem's house of learning to Ever, and then from Ever's to Avraham's.
Indeed, the Seder Olam Rabbah, 1 writes that aside from learning from/attending to his grandfather Avraham, Yaakov attended to Shem for fifty years(!):
יעקב שימש את אבינו אברהם ט"ו שנה, ואת שם חמשים שנה
Yaakov attended Avraham our forefather for 15 years, and Shem for 50 years.
Another angle to this question is that they excelled in different things i.e. what Shem and Eiver were 'good' at was not necessarily the same as the Avos and as a result, they stuck to what they were good at. As such, they didn't partner in the sense you ask because they had differing strengths.
I saw the following thought brought in Torah Tavlin for Parshas Lech Lecha 5782
The pasuk in Lech Lecha 12:5 writes:
וַיִּקַּ֣ח אַבְרָם֩ אֶת־שָׂרַ֨י אִשְׁתּ֜וֹ וְאֶת־ל֣וֹט בֶּן־אָחִ֗יו וְאֶת־כָּל־רְכוּשָׁם֙ אֲשֶׁ֣ר רָכָ֔שׁוּ וְאֶת־הַנֶּ֖פֶשׁ אֲשֶׁר־עָשׂ֣וּ בְחָרָ֑ן וַיֵּצְא֗וּ לָלֶ֙כֶת֙ אַ֣רְצָה כְּנַ֔עַן וַיָּבֹ֖אוּ אַ֥רְצָה כְּנָֽעַן׃
Avram took his wife Sarai and his brother’s son Lot, and all the possessions that they had amassed, and the persons (lit. souls) that they had made/acquired in Charan; and they set out for the land of Canaan. And they came to the land of Canaan.
The Rosh Yeshiva and member Degel Hatorah Moetzas Gedolei Yisrael, HaRav Baruch Mordechai Ezrachi shlita brings in his Bircas Mordechai (from p. 134) the Tanna D'Vei Eliyahu which writes how Shem tried to influence the world for 400 years without any joy. It was only when Avraham came on the scene that he was able to 'create souls'.
The Torah Tavlin concludes:
Why was Shem not successful like Avraham? Because different people have different talents. The Avos had the unique ability to create souls. Shem and Eiver lacked that ability. At the same time, Shem and Eiver did have the ability to create Avos. All of them learned how to be avos in Yeshivas Shem V'Eiver. Sometimes you need a Yeshiva in order to create the superstars who will lead the next generation.