I just thought of a theory about Jack's dad. What if he was a soldier? Could explain him 'leaving' June and Jack, why he never returned and why June worries so much when she feels things are beyond her control. Her anxiety for Jack seems to increase when she sees him 'leaving' her behind too. Maybe Jack's dad was involved in and died fighting the Decepticons in the years prior to the start of the series? June and Jack wouldn't know what he died fighting against. Just that he fell in battle. Wouldn't it be a shocking revelation later on if they finally discovered that Jack's dad had perished fighting Cybertronians. Maybe Jack could even have a reason then to resent both the Autobots and the Decepticons for bringing their war to Earth and taking his father away from him and his mum!