As we read through this, keep in mind what we saw in Daniel 7. I propose to you that this vision in Revelation is a magnification of what happened when the Son of Man ascended and was brought before the Father, resulting in the Father giving Him dominion and glory and a kingdom. Notice how well it matches up:
That makes it even more specific. The kings who are going to govern under Christ are not only those who come up in the first resurrection but they are also identified as those who are "the redeemed" by the blood of the Lamb (as we read, just a little bit earlier), and that the reign is going to be on earth.
