Two Headed Egg

[West Coast Jungle]

Looking at the picture again that might be what happened if they are not twins. The egg they pipped from looks like it's on top of another one. Maybe the baby on the bottom got through it's egg and just kept going up?

That would be my guess as well, explains why they're "normal" sized!

If you look at the original picture you can see there is another egg under the one with the two heads, the lower hatchling cut into the upper egg and both were emerging from the upper egg at the same time like twins would. Although you can see the lower egg you don't see any evidence that it had hatched until the upper egg eventually collapsed on it.