There are clues in Scripture providing the conclusion.
The two witnesses are also called "lampstands".
The Revelation gives the interpretation of "lampstand" as being a "congregation".
They are congregations,
working together to preach the Testimony of Jesus Christ,
which is His Gospel.
Then Christ Himself said He had another flock to bring into the one fold,
and for this,
He sent Paul the Apostle of the Gentiles.
As Peter was recognized as the Apostle of the Jews,
and Paul as that of the Gentiles;
as Ephesians speaks of making the two,
one new man,
reconciled through the cross,
that is,
through what Christ finished on the cross,
which was the remission of sin,
and thus the justification of His two flocks,
bringing them into His Fold;
so the two witnesses,
being congregations,
are these two flocks,
the Elect from among the Jews,
and the Elect from among the Gentiles.