cross or did only one of them mock him and the other come to his defense?
The three texts are Mat 27:44, Mk 15:32 and Lk 23:39-42. Matthew and Mark say the same thing:
The robbers who had been crucified with Him were also insulting Him with the same words.
39One of the criminals who were hanged there was hurling abuse at Him, saying, "Are You not the Christ? Save Yourself and us!"
40But the other answered, and rebuking him said, "Do you not even fear God, since you are under the same sentence of condemnation?
41"And we indeed are suffering justly, for we are receiving what we deserve for our deeds; but this man has done nothing wrong."
42And he was saying, "Jesus, remember me when You come in Your kingdom!"
Luke 23
It appears that they took about three hours to die, and during this time one of the two robbers repented.