Continuity mistake: When Richard Harris is talking to his daughter about her future, the fire lamp behind them changes positions between shots. (00:20:15)
Continuity mistake: At the very start of the film when we see Maximus for the first time, he is talking to his friend Quintus. Two boys run past, yet when it cuts to another shot they have vanished. We should have been able to see them at least running off in the background somewhere. (00:03:40)
Continuity mistake: After the Gladiators are victorious at the Battle of Carthage, Maximus reveals his identity to Commodus. The time seems to change from sunset to high noon a number of times. The crowd shots are at noon, the close ups are clearly made with the sun on one side of their faces. (01:27:20)
Continuity mistake: When Lucilla is talking with Gracchus and Gaius about Commodus and she says "He must die", we see Gracchus in the background looking at Lucilla. When it cuts he is looking down lifting his head to look at Lucilla. (Extended version only). (01:21:10)
Continuity mistake: At the Coliseum when the crowd is placing bets, you can see a man writing on a blackboard. He stops writing and turns around. When it cuts back to a closeup he turns around again. (01:15:05)
Continuity mistake: In the middle of the film, just after the last gladiator match in the Roman province arena, Maximus goes to see Proximo. In one particular shot we see Proximo walk away and Maximus turn his whole body to face him, yet in the following shot, it is just his head that is turned. (01:07:05)
Continuity mistake: When Commodus and Lucilla are lying in bed, after Commodus tries to seduce her for a kiss, he lowers his arm and says "You know I love you". When it cuts he suddenly has his hand lying on her shoulder. (01:57:40)
Continuity mistake: When the gladiators have won inside the coliseum for their first battle, Commodus goes to see Maximus in the arena. In the previous shot, Maximus gets off of a white horse, yet in the following shot, the white horse is at the bottom of the screen with Maximus and the other gladiators some distance away. (01:25:35)
Continuity mistake: After the final fight scene when Maximus is on the ground, Lucilla is kneeling above him. When her face is shown, it is blocking out the sun. And yet, when the shot shows Maximus's face, there is no shadow. (02:18:50)
Continuity mistake: When Maximus and the other gladiators are walking up to the Coliseum in Rome, the black guy walking with him is about 2 to 3 feet away from him. When the camera cuts to a face shot, they are shoulder to shoulder. (01:14:35)
Continuity mistake: When Aurelius says "Enough with politics. Let's pretend I'm a father." to Lucilla, she smiles and looks down. When it cuts she is still looking down, but in the next shot she is suddenly facing Aurelius again. (00:20:20)
Continuity mistake: When Maximus chops the head off the German at the beginning of the movie, his sword is supposed to be stuck to the tree. However after he has chopped the head off you can for a second see the sword in his hand before we get to the shot where the sword is stuck to the tree. (00:09:40)
Continuity mistake: Before they attack the Germanians, Maximus says "Strength and honor" to Quintus and he replies. Then Quintus says the same to another soldier who is facing him. When it cuts the soldier is suddenly walking away. (00:05:10)
Continuity mistake: At the end of the movie when Maximus is lying dead, and Lucilla asks who will help carry his body. Her bracelet on her arm is positioned differently than right before she asks the question when she is looking around at the crowd. (02:20:10)
Continuity mistake: In the final battle, there are about 20 or something Praetorians on the platform when it moves up. But when you see the platform coming up to the arena, there are suddenly enough to form the "tortoise" position; and then they have multiplied in order to arrange the circle around Commodus and Maximus (about 45 Praetorians). (02:13:05)
Continuity mistake: When the Germanian leader is stabbed the first time he holds his weapon with both hands. When it cuts it's only in his right hand. (00:10:25)
Continuity mistake: When Quintus tells the soldier to move the catapult he is standing right behind Maximus. When it cuts, he is further away from Maximus. (00:03:50)
Continuity mistake: The weather during the battle against the Germanians changes almost every second: Hard snowfall, soft snowfall, almost sunshine, soft snowfall, etc. (00:10:35)
Continuity mistake: At the end of the first battle inside the Colosseum, Commodus goes out to see Maximus, yet when he first enters the arena's floor, the distance from him to Maximus changes three times during shots. For example, when he first goes through the gate, it cuts to Maximus, then back to Commodus and he is just coming out the gate again, yet in the previous shot he came out the gate. (01:26:15)
Continuity mistake: The first time Maximus is about to fight as a gladiator we see him grabbing some dirt in his right hand and pouring it into his left hand. When it cuts we can see both his hands covered in dirt before he start rubbing his hands, as if he already has rubbed his hands in a previous scene. (00:52:55)
Chosen answer: No, they are full brother and sister. They both had the same mother and father. Incest was not exactly normal at that time, but it stretches back within the imperial families as far as Caligula and possibly earlier. There is no evidence to suggest that the real Commodus was attracted to his sister, it was probably just included in the film in order to make the character seem more disturbed, and also as another reason why he would be Maximus' enemy (Maximus and Lucilla were, after all, once lovers).
The Doctor