The biblical study on The Four Crucified with Christ teaches much of how to study the Bible and many times that traditions contradict the truth. There are many things commonly taught about Easter that are not what the truth of God’s magnificent Word teaches. The four crucified with Christ is just one of them and it is one I have diligently worked through the Word for myself. John Schoenheit, one of the finest biblical researchers and teachers I have known says it much better than I can. The full article and video can be found here. Enjoy. — Augie
One difference that we should note as we read the crucifixion records is that Matthew 27:38 (ESV) and Mark 15:27 (ESV) clearly state that there were “two robbers” crucified, while Luke 23:32 (ESV) says there were “two criminals” crucified. Other versions such as the NIV, NASB, and RSV also use the translations “robber” and “criminal,” while other versions use different words, such as “thief” and “malefactor” (KJV). While it is clear that a robber is a criminal, and so these might be the same set of two men, it should nevertheless catch our attention that the Bible uses different Greek words, lēstēs (robber) and kakourgos (criminal) to describe them, so perhaps they are different sets of men. It becomes much more likely that they are two different sets of men when we add the piece of evidence that Matthew says the robbers (lēstēs) reviled Christ but Luke says that only one of the criminals (kakourgos) did.
Matthew 27:44 (ESV) 
And the robbers who were crucified with him also reviled him in the same way.
Luke 23:39 and 40 (ESV)
(39) One of the criminals who were hanged railed at him, saying, “Are you not the Christ? Save yourself and us!”
(40) But the other rebuked him, saying, “Do you not fear God, since you are under the same sentence of condemnation?