C.M.
My son started waking up earlier and earlier around age two as well. I figured part of the problem was that he would wake up and assume that it was time to get up. What we did is, he has a nightlight, which we put on a timer. As he can't tell time, this became a signal for him. When the light is on, it is bedtime, he is to be in bed. When the light is off, it is daytime, he is allowed to get up. It took a little while to get him used to it. He would get up, but if the light was on, we would put him back to bed and remind him it is not time to get up until the light is off. It's has worked well for us. He has even been known to sleep in on rare occasion. :-)