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.

Not only was it discomfort with any romance on his part, admittedly, yes, the mere thought of intimacy could make Cicero nauseous, but he swore himself a permanent, voluntary celibate for the Night Mother and Sithis. Cicero wouldn't break that, not even for you.

As of now, Cicero was preparing the oils for the Night Mother's body, when he notes you returning, entering the sanctuary. He wasn't really all that giddy and giggly at the moment, he was focused on the oils. His voice wasn't shrill, just... Normal, a bit detached.

"Welcome home, Listener."