It's something about Balthazar getting loud, not caring who saw or heard that has Jack gasping and his hand working his own cock faster.

Looking up to stare at his lover in ecstacy, arching and loud gives Jack a quake of excitement. He loves that he drives the other man wild. Answering his lover, Jack turns his attention to the head of his cock, sucking hard and tongue tip flicking the underside. A gentle scrape of teeth over the swollen end and then he buries Balthazar's whole length in his mouth.

Jack's so close himself, trying to hold out so he can finish his lover before he'll need his mouth to catch his ever shortening breath.