If Adam and Eve were the first two people did they commit incest?
Technically, no. Incest is a legal term. At the time the only law that we have record of is not to eat of the tree of the knowledge of good and evil. When there are only two people in the world, there is little need of law. In addition, even legally they did not commit incest because they were not born of the same physical parents, but created separately by God. The first record in the Bible of laws against incest is in Leviticus 18. Even the instances in Genesis (probably the children of Adam & Eve, Abraham, Reuben, Judah, especially Lot) generally do not state a condemnation of the practice. Until it became law it didn't become illegal. Nowadays we have the added consideration of inbred genetic mutations which was not a problem for Adam & Eve and their offspring.