Evidence from scripture tells me this is Lucan redaction. He or someone before him has probably expanded Mark’s narrative.
John narrates two men were crucified beside Jesus and nothing else, which is consistent with his magisterial presentation of Jesus’s death (which he was in full control of at all times).
19:18 There they crucified him, and with him two others, one on either side, with Jesus between them.
Mark 15:27-32 tells us only that the two crucified next to him taunted and mocked him as well:
27 And with him they crucified two rebels, one on his right and one on his left.[d] 29 Those who passed by derided[e] him, shaking their heads and saying, “Aha! You who would destroy the temple and build it in three days, 30 save yourself, and come down from the cross!” 31 In the same way the chief priests, along with the scribes, were also mocking him among themselves and saying, “He saved others; he cannot save himself. 32 Let the Messiah,[f] the King of Israel, come down from the cross now, so that we may see and believe.” Those who were crucified with him also taunted him.
Matthew follows Marks account pretty slavishly here (Marcan priority) in 27:38-44. Note the two bandits both taunt Jesus:
38 Then two rebels were crucified with him, one on his right and one on his left.39 Those who passed by derided[n] him, shaking their heads 40 and saying, “You who would destroy the temple and build it in three days, save yourself! If you are the Son of God, come down from the cross.” 41 In the same way the chief priests also, along with the scribes and elders, were mocking him, saying, 42 “He saved others; he cannot save himself.[o] He is the King of Israel; let him come down from the cross now, and we will believe in him. 43 He trusts in God; let God deliver him now, if he wants to, for he said, ‘I am God’s Son.’ ” 44 The rebels who were crucified with him also taunted him in the same way.
Luke changes it up a little as he copied Mark. Now one of the bandits Matthew and Mark claim taunted Jesus along with everyone else acknowledges him and is saved. This is a problem.
39 One of the criminals who hung there hurled insults at him: “Aren’t you the Messiah? Save yourself and us!”
40 But the other criminal rebuked him. “Don’t you fear God,” he said, “since you are under the same sentence? 41 We are punished justly, for we are getting what our deeds deserve. But this man has done nothing wrong.”
42 Then he said, “Jesus, remember me when you come into your kingdom.[d]”
43 Jesus answered him, “Truly I tell you, today you will be with me in paradise.”
Personally, I’m not interested in “there were two people next to Jesus that taunted him then two more were brought that 3 of the gospels don’t write about but Luke knows of. Nor am I interested in “the two both mocked him at first but one thief changed his mind” and none of the other three gospels thought to mention that and Luke omitted the former.
Those reek of uncritical harmonization. Building a theology based off that one verse when the other gospels seemingly narrate a different version of that story is a house built on sand. I do not even deny deathbed conversions. But for those who accept Christ and live to a ripe old age, works clearly seem to be required by Jesus and parts of scripture.