Another interpretation: "And these are the names of the sons of Israel who came into Egypt, Jacob and his sons" (Exodus 1:1). "Each man and his household" (Exodus 1:1) teaches that Jacob did not go down to Egypt until there were eight in the line of Perez, and Hezron and Hamul were among them, this one a year old and that one two years old, and he matched them with wives. "Each man and his household" they came.
Each Man and His Household Came Down to Egypt
Yalkut Shimoni on Torah 162:5
דָּבָר אַחֵר וְאֵלֶּה שְׁמוֹת בְּנֵי יִשְׂרָאֵל הַבָּאִים מִצְרָיְמָה יַעֲקֹב וּבָנָיו. אִישׁ וּבֵיתוֹ, מְלַמֵּד שֶׁלֹּא יָרַד יַעֲקֹב לְמִצְרַיִם עַד שְׁמוֹנָה לְפֶרֶץ וְחֶצְרוֹן [וְחָמוּל] זֶה בֶּן שָׁנָה, וְזֶה בֶּן שְׁתֵּי שָׁנִים, וְזִוֵּג לָהֶם נָשִׁים. אִישׁ וּבֵיתוֹ בָּאוּ.