You are not alone.
My kids both do this. One is 3, the other is 14 months. Occasionally they will sleep until 6:15, but usually they are up much earlier. The hard part is they wake each other up, even when not sleeping in the same room.
It also goes in cycles. But the cycle is never "sleep til 8". Around here it does not matter when they go to bed and it does not matter if/when they nap. (If the three year old naps, forget it, we up til 10 o 10:30 at night AND awake at 5). Our day is so long that the night time routine helps a lot because it lets me know the end of the day is in sight.
Some things that have made it worse: making morning fun time. On really brutal mornings I will turn on the TV to kiddie stuff, but for the most part, I try not to, so they don't expect morning to be like that each day. I used to give snacks thinking, oh! they must be hungry, but that usually backfires too.
Stuff that makes it a little better: getting naps for me, even if they don't nap, keeping breakfast at a set time, so it is not feeling like I am just the food and snack getter at 5 in the morning, working to help them sleep through the night. (the 14 month old does not yet). Night wakings are harder for me than waking up early, and neither is very easy, if that makes sense. (I am not a morning person and my body has never adjusted to this schedule). So for me it has been important to get my daughter to sleep on her own. They are so active though that if they are both in the bed, they don't sleep anyway, no matter what time it is. Another thing that helps is telling my daughter it is early and not time to start the day yet, to let her know that it is early and not time to start the day yet. It sounds cruel and I would love to be the mom doing crafts at 6, but I just can't. No matter when they get up, breakfast is at 7, dressing is after that, and then the day starts. Period. It is a struggle and hard, but I found when I was not "mommy on the spot" with the wakings, as in would you like juice? a snack? here, let me do _____for you, at yes 4:30 or 5 in the morning, I was better able to handle the cycles. If they are really hungry I offer crackers, but for a while there I was making food early or starting our day super early, and it was not working well.
Good luck. As you can see, you are not alone.