Jace was definitely enjoying the results so far of figuring out what turned Alec on.

The way Alec was begging, Jace was pretty sure he just wanted more, but he couldn't resist the urge to tease him, just a little. The tug on his hair made him moan again, swallowing around Alec's cock. He pulled his mouth free with a slow slide of his lips, and then turned his head to bite into the inside of Alec's thigh, a sharp nip of his teeth and then kissing the sting away. "Alec. Sweetheart. You gotta use your words if you want something, my mouth is busy," he grinned up at him.