Even without Harry's notices to the DA, (which Jack had been in now, for exactly five minutes. Brought in by Colin) Jack wouldn't have been able to sleep. There was just too much going on for him at the moment and it had left him unable to shut his eyes for more than a minute without thinking about Melina or Colin or--now--everything else that had happened. His parents were safely far from involved with the Ministry and so he felt no need to worry.
When he heard someone on the stairs, heading down from the dorms to the common room, decided to follow. He put his trousers back on and headed down to see what was going on.
"Dennis?" He glanced from the familiar boy to Vic and then walked over to where both of them sat. "Can't sleep either, then?"