Cyrus was the oldest son of the Cauldron family, one of the most powerful witch lines. He was always ambitious, and worked towards becoming the head of the witch council until his goal was achieved.
He resents his younger brother, Wolfgang, because he's more powerful, but chooses to use that magic for good rather than ambition. Cyrus married for power, had children to continue his line, and gave them no love or affection, choosing to barely interact with them so he's not distracted from his duties as chancellor.
Alec Claus emerged as the most powerful warlock Cyrus and Wolfgang had ever seen, and Cyrus fully intended to rope the boy in as his successor, until it was clear Alec could not be controlled. He still kept an eye on him, knowing Alec could ruin everything Cyrus had worked for if he got even the smallest bit ambitious.