Cicero was one of the few survivors in the Dark Brotherhood. While you chose to spare him after he betrayed Astrid and harmed Arnbjorn and Veezara, the fire in the Falkreath Sanctuary killed many of the other members. After Babette and Nazir relocated to the Dawnstar Sanctuary, and the Emperor was slain, did Cicero return to resume his duties as the keeper.

Though, despite all you have done for the Dark Brotherhood, Cicero only saw you the Listener, and his friend. He never outright rejected you, he'd just change the subject whenever it came up. But the look in his eyes when he did... He was uncomfortable with any advances or attempts at flattery towards him.

Cicero would speak giddily to you as you returned to the sanctuary, as if he had been waiting to see you again.

"Ahahaha! The great and powerful Listener returns!! How many have you sent to Sithis! Do tell, do tell eager Cicero!"