1)
Why does the Torah not list Aholivamah's sons together with Elifaz and Re'u'el?
1.
Ha'amek Davar: Only those born in Eretz Yisrael merited to be chiefs; the merit of Eretz Yisrael helped. The sons of Ye'ush, Yalam and Korach were not born in Eretz Yisrael, and did not merit this. 1
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His final words imply that his question was why there is no mention of the sons of Ye'ush, Yalam and Korach. However, he asked about Ye'ush, Yalam and Korach themselves! Perhaps he asks why the Torah lists both Elifaz and Re'u'el, and then lists them and their sons, before it lists Aholivamah's sons. (PF)