He was the top mage of the Stormwind kingdom. At the same time, he was a renowned member of the Council of Tirisfal. In the reign of King Landen Wyrnn, he happened to encounter one of the Guardians of Trisifal at the time, Magna Aegwynn, and even successfully led her into his hands. But actually, from the very beginning, Aran and Aegwynn's meeting was a scheme set up by the latter. In order to successfully produce an outstanding child, the experienced Aegwynn charmed Aran. Aegwynn took advantage of the situation, finally getting Aran onto bed, and she gave birth to the later Medivh.
The plan worked as expected. After Aegwynn had her showdown with Aran, she left Stormwind City. After the child was born, Medivh was sent to Aran's hands, but she herself escaped to the ends of the earth.
Anger and shame filled Aran's heart, but Medivh was his own flesh and bone, so he rarely turned showed anger and hate onto his own child.