"I don't define one person as sleeping around." Jace said, his temper getting the best of him in that moment, regretting the words as soon as they were out of his mouth. "But that's not the point is it?" He said, pushing his hair back from his face as he moved to sit in a chair facing his brother. "I met Damien before I started seeing you and Mark. I didn't think that it would be a problem to keep sleeping with him every now and then. I should have known better." Not quite an apology but it was as close as he could get right then.
His head jerked up at that question and he stared at Alec, open mouthed for a second before answering him. "NO!" His word came out louder than he'd expected, yelling almost. "By the angel - no." He said, fear at losing what they'd found here flooding him.