Genesis: War of Kings

The person called “אַרְפַּכְשַׁד” was one of kings in the story Avraham’s “War of Kings” (בראשית), and he was at war with “מַלְכִּי־צֶדֶֿק” (whom the sages say  is “שם בן נח“). That is “Shem son of Noah”.

Shem (שם בן נח) is the father of אַרְפַּכְשַׁד according to our tradition. That means it was a legitimate Father-Son conflict. This also means that Avraham Avinu was helping one of his own living ancestors to fight one of his other living ancestors.

Sources: Targum Yonasanand Targum Yerushalmi – B’reishis 14:18–20. 
Talmud Bavli – tractate Nedarim 32b.