well when they start performing supernatural acts as it is written of them , that they will do. Then we can say they maybe are the two witnesses.
Revelation 11:
3 And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth.
4 These are the two olive trees, and the two candlesticks standing before the God of the earth.
5 And if any man will hurt them, fire proceedeth out of their mouth, and devoureth their enemies: and if any man will hurt them, he must in this manner be killed.
6 These have power to shut heaven, that it rain not in the days of their prophecy: and have power over waters to turn them to blood, and to smite the earth with all plagues, as often as they will.
The only two ever to perform these kinds of acts where Elijah & Moses. No one ells. The same two, that appeared with Christ Himself on the mount of transfiguration .
Luke 9:
29 And as he prayed, the fashion of his countenance was altered, and his raiment was white and glistering.
30 And, behold, there talked with him two men, which were Moses and Elias-( Greek for Elijah) :
31 Who appeared in glory, and spake of his decease which he should accomplish at Jerusalem.
Of Moses :
Exodus 7:20
King James Version (KJV)
20 And Moses and Aaron did so, as the Lord commanded; and he lifted up the rod, and smote the waters that were in the river, in the sight of Pharaoh, and in the sight of his servants; and all the waters that were in the river were turned to blood.
Again of Moses :
Exodus 10:13
King James Version (KJV)
13 And Moses stretched forth his rod over the land of Egypt, and the Lord brought an east wind upon the land all that day, and all that night; and when it was morning, the east wind brought the locusts.
Of Elijah :
1 Kings 17:1
King James Version (KJV)
17 And Elijah the Tishbite, who was of the inhabitants of Gilead, said unto Ahab, As the Lord God of Israel liveth, before whom I stand, there shall not be dew nor rain these years, but according to my word.
Again of Elijah:
1 Kings 18:36-39
King James Version (KJV)
36 And it came to pass at the time of the offering of the evening sacrifice, that Elijah the prophet came near, and said, Lord God of Abraham, Isaac, and of Israel, let it be known this day that thou art God in Israel, and that I am thy servant, and that I have done all these things at thy word.
37 Hear me, O Lord, hear me, that this people may know that thou art the Lord God, and that thou hast turned their heart back again.
38 Then the fire of the Lord fell, and consumed the burnt sacrifice, and the wood, and the stones, and the dust, and licked up the water that was in the trench.
39 And when all the people saw it, they fell on their faces: and they said, The Lord, he is the God; the Lord, he is the God.
etc.
Until you see two do these two things, then they are not the two witnesses . Keep reading on in Chapter 11 of the book of Revelation.