Another interpretation: "And these are the names of the sons of Israel who came into Egypt" (Exodus 1:1). But were not Ishmael and Isaac brothers, and Esau and Jacob brothers? Why then did neither Ishmael nor Esau go down? Rabbi Eleazar said: To what may the matter be compared? To one who borrowed from the king. After some days the borrower died and left two sons. The king found one of them serving before him, and the other had fled. He said to the one serving before him, "From you I will collect the whole debt that your father owed me." He said before him, "Because I served before you I have lost out." He said to him, "By your life, I will give you a great reward. When that other one is caught, I will hand him over to you as a slave." So too in the time to come, "And they shall possess the South, the mountain of Esau" (Obadiah 1:19). And further, "And you shall serve your brother" (Genesis 27:40). Not only did he not serve him, but he made him serve through every kind of trouble, and "as he has done, so shall it be done to him" (Leviticus 24:19).
Why Jacob's Children Descended and Esau's Did Not
Yalkut Shimoni on Torah 162:6
דָּבָר אַחֵר וְאֵלֶּה שְׁמוֹת בְּנֵי יִשְׂרָאֵל הַבָּאִים מִצְרָיְמָה, וַהֲלֹא יִשְׁמָעֵאל וְיִצְחָק אַחִים הָיוּ, וְעֵשָׂו וְיַעֲקֹב אַחִים הָיוּ, וְלָמָּה לֹא יָרְדוּ לֹא יִשְׁמָעֵאל וְלֹא עֵשָׂו, אָמַר רַבִּי אֶלְעָזָר, לְמַה הַדָּבָר דּוֹמֶה, לְאֶחָד שֶׁלָּוָה מִן הַמֶּלֶךְ, לְאַחַר יָמִים נִפְטַר הַלֹּוֶה וְהֵנִיחַ שְׁנֵי בָּנִים, וּמָצָא אֶחָד מְשַׁמֵּשׁ לְפָנָיו, וְאֶחָד בָּרַח, אָמַר לְאוֹתוֹ הַמְּשַׁמֵּשׁ לְפָנָיו, מִמְּךָ אֲנִי גּוֹבֶה כָּל חוֹבִי שֶׁנִּתְחַיֵּב לִי אָבִיךָ, אָמַר לְפָנָיו, לְפִי שֶׁשִּׁמַּשְתִּי לְפָנֶיךָ הִפְסַדְתִּי, אָמַר לוֹ, חַיֶּיךָ שָׂכָר גָּדוֹל אֲנִי נוֹתֵן לָךְ לִכְשֶׁיִּתָפֵשׂ אוֹתוֹ אֲנִי מוֹסְרוֹ לְּךָ לְעֶבֶד. כָּךְ לֶעָתִיד לָבֹא "וְיָרְשׁוּ הַנֶּגֶב אֶת הַר עֵשָׂו". וְעוֹד (בראשית כז, מ) "וְאֶת אָחִיךָ תַּעֲבוֹד, לֹא דַי שֶׁלֹּא עַבָדוֹ, אֶלָּא שֶׁהֶעֱבִידוֹ בְּכָל מִינֵי צָרוֹת" (ויקרא כד, יט) "כַּאֲשֶׁר עָשָׂה כֵּן יֵעָשֶׂה לּוֹ".