Do the Sources anywhere specifically stress the importance of family in general? Maintaining ties with family members, even though they may live far away, seeking long-lost cousins, having reunions, cultivating and prioritizing these relationships, and the like?
There certainly was a precedent to maintain family connection in terms of the instructions Avraham gives Eleizer:
אִם־לֹ֧א אֶל־בֵּית־אָבִ֛י תֵּלֵ֖ךְ וְאֶל־מִשְׁפַּחְתִּ֑י וְלָקַחְתָּ֥ אִשָּׁ֖ה לִבְנִֽי׃
but you shall go to my father’s house, to my kindred, and get a wife for my son.’
True that the main concern was that he didn't want his son to take a wife from the daughters of Cana'an. But, technically, there were others living in Padan Aram, right? Avraham could have instructed to find a non-Canaanite woman from Padan Aram or from any other place. It seems that he had faith that a good match would emanate from his own family, despite not having had contact with them for numerous years, most likely.
Similarly, Rivkah sends Ya'akov back to her father's home to find a wife from her own family. She too, probably had little or no contact.
Yosef insists that his father bring all the family - all the children and grandchildren to Egypt. Yes, of course, the motive was the famine. But, he does say, "You shall be close to me", and there's probably a sense that he wanted physical closeness of his family.