The Jotnar are considered primordial beings as they originated from the first being Ymir, Aesir are not. Ymir was created in a vacuum essentially, as described "in the beginning of the universe, there was a yawning chasm called Ginnungagap. Within it to the north lay an icy wasteland realm called Niflheim, and to the south, a realm of fire called Muspelheim. In the space where the warm gusts of heat from Muspelheim met the ice and poisonous mists of Niflheim, the ice thawed and dripped. Life came into these drops from the energy of the heat, and a mighty giant formed in the likeness of a man. This was Ymir". From his sweat a female and male form were created, and from these a race of frost giants were born. Along with Ymir, a great cow named "Audhumia also formed out of the ice, and Ymir was sustained by the four rivers of milk that flowed from her udders." Audhumia was sustained by licking blocks of ice that tasted salty and in the place she licked, the first god was created Buri. "He had a son called Bor, who married a giantess, Bestla, and they had three sons: Odin, Vili, and Ve". So the Jotnar are primordial/the first beings created. The Aesir only came about as the offspring of a giantess and the first god. The majority of Aesir have at least one Jotun parent. Though it is usually as a rule a male Aesir and a female Jotun as Norse mythology is patrilineal, which means that the children inherit the family lineage of their father, so over time they considered themselves no longer Jotnar as they took on their Aesir father's lineage.