Do you realize that these four living creatures Ezekiel saw in prophesy in the very midst of Jesus' throne (Rev 4:6) are redeemed humans? Rev 5:9 And they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation; (And they are with Jesus in heaven prior to the part of the tribulation known as the temptation to come upon all the earth - Rev 3:10).
There are many Christians in heaven who have been redeemed by the blood of Jesus now and the tribulation hasn't taken place yet nor any rapture.Ref (with Jesus prior to the tribulation) Yet I still get the sense these elders are older than anyone born after Jesus came down to us. Example Moses, Abraham, Jacob, Joseph ,Enoch, Daniel any many more we don't even know about. That they would have been chosen by grace before they did good or bad like Paul . The seats given to those they would have been prepared for by grace. For only Jesus was found worthy of honor and power and glory.