My 2 year old wakes up at the same time every night and is awake for 2-4 hours. could he have some sort of insomnia?

Yes and no: It depends on how you define insomnia. He technically has a sleep cycle disorder, which you could call insomnia. It doesn't really matter what you call it, but what you can do about it. He needs to get his body into a better sleep cycle - right now his cycle is to sleep for a few hours and then be up for a few hours. Not good for you or him. Talk to doc about appropriate sleep hygiene for him.