The Man in the Iron Mask

France is under the reign of the militaristic King Louis XIV (Leonardo DiCaprio), who is bankrupting the country with his unpopular wars. When starving peasants in Paris start rioting for food, he responds by ordering his chief adviser Pierre to send them rotten food - although he later orders Pierre executed for this and all rioters killed. Meanwhile, the king continues to wallow in hedonistic luxury and seduce a parade of women. The legendary Three Musketeers have retired from their posts: Aramis (Jeremy Irons) is now a priest of the Jesuits; Porthos (Gérard Depardieu) is a frequent visitor to Parisian brothels; Athos (John Malkovich) has a son named Raoul (Peter Sarsgaard) who has just returned from the war and signifies his application to join the musketeers, like his father who once served with pride and honor. Meanwhile, Athos gives Raoul his wife's ring, saying that the only lady worthy to wear it is the one that Raoul loves. The lucky girl he loves is Christine Bellefort (Judith Godrèche) whom he intends to propose for marriage. At a festival, the two lovers are greeted by an older D'Artagnan (Gabriel Byrne), who is still in the service of the King as Captain of the Musketeers, striving to retain the esprit de corps of the old days. D'Artagnan wishes Raoul and Christine luck, but just before Raoul can propose, the king's eyes fall on Christine. He arranges for Raoul to be returned to combat, where he is killed by the Dutch cannons while leading ground troops in an attack en-masse. The news of his son's death reaches Athos, who, in a fit of rage, proceeds to the king's palace to seek vengeance. He injures two musketeers before D'Artagnan overpowers him on the Palace grounds. This puts a severe strain on Athos's friendship with D'Artagnan, who he now sees as a traitor for siding with his son's killer.In the wake of Raoul's death, Louis invites Christine to the palace where she sleeps with him, grateful for the medical assistance his doctors have given to her mother and sister. When Louis orders Aramis to find and execute the secret leader of the Jesuit order, Aramis sets in motion a plot to overthrow the king with the help of his old comrades, for this secret leader is none other than Aramis himself. Only Athos and Porthos agree to the plan; D'Artagnan refuses to betray his oath of honor and allegiance to the king. The three former Musketeers sneak into an island prison and arrange the escape of a mysterious prisoner: a man in an iron mask. They replace him with a corpse in a matching iron mask and, pretending it is plague ridden, burn it so the guards will not know the face behind the iron mask. They take the young man to a safe house in the countryside and unmask him: he is Philippe (Leonardo DiCaprio), the identical twin of King Louis. While he is identical to his brother, Philippe is compassionate and gentle. Aramis reveals that Philippe was sent away by his father, King Louis XIII, to save France from dynastic warfare. Later, when Louis discovered Philippe's existence, he was too superstitious to have his own brother murdered; so instead, he devised a way to keep him hidden: the iron mask. Aramis, at time still serving as a musketeer and clad in black uniform, the only thing Philippe remembers, was the one who took him away to prison, an act which has haunted him ever since.Meanwhile, King Louis succeeds in seducing Christine completely, claiming that he ordered Raoul to be placed far from the battlefront. Christine receives a letter from Raoul, predicting his death and saying that he forgives her for becoming the king's mistress. Whilst in bed with Louis, Christine admits that she still loves Raoul and that she is not in love with him. Enraged, Louis forsakes Christine.Athos, Porthos, and Aramis teach Philippe how to act like royalty, so he may replace Louis as king. Together they abduct Louis during a fancy dancing ball. Before his absence is revealed, Philippe takes his place. However, Philippe's good nature gives him away when he helps one of the dancing ladies up from the floor after she falls over and spares Christine's life when she storms in and openly accuses him of murdering Raoul (having learned this from a letter sent by Louis' General), promising to make amends for wronging her. D'Artagnan realizes something is amiss, orders all palace musketeers to be on full alert, and personally escorts Philippe to the underground dock. They arrive just as Athos, Porthos, and Aramis are about to sail for the Bastille with Louis. The men collectively decide to make a trade for the brothers' lives; however, Philippe is re-captured in the ensuing chaos of their escape.Afterwards, D'Artagnan is stunned to learn that Philippe is Louis' brother and pleads with Louis to spare his life. Louis at first refuses, but Philippe bluffs that he is more terrified of the iron mask than death itself, begging to be executed rather than sent back to prison. Louis orders him placed in the Bastille and once again in the mask. In the aftermath, Christine is found to have hanged herself from her bedroom window.Athos, Porthos, and Aramis brush off their old musketeer uniforms, becoming The Three Musketeers again and, with D'Artagnan's help, break into the Bastille prison and escape with Philippe. Louis, however, has prepared an ambush. Fortunately, the narrowness of the corridor and the guards' respect for D'Artagnan, their captain, prevents them from overwhelming the four Musketeers with their numbers, although the five men eventually end up trapped against a barred door at the end of the corridor with no way out. Determined to save his friends, Philippe offers to give himself up in exchange for their lives. D'Artagnan refuses, revealing to everyone's astonishment, that he is actually the twins' father, having had an affair with Queen Anne, and that it was out of fatherly devotion that he served Louis, not loyalty. D'Artagnan adds that he feels the pride as a father for the first time upon learning that Philippe is also his son.The four Musketeers and Philippe make a final charge at Louis' front line. Their "magnificent valor" stuns the soldiers into immobility, angering Louis and forcing him to repeatedly shout orders to fire. He lays his hands on one of the soldiers' muskets and it goes off, setting off the rest, with many of the men shutting their eyes or looking away out of reluctance. The smoke clears to reveal the five men still standing; all the shots, barring a few flesh wounds, missed.An enraged Louis lunges toward Philippe and tries to stab him. D'Artagnan jumps between them and is fatally wounded when Louis stabs him in the back. Philippe knocks Louis down and begins to strangle him, but D'Artagnan, with his dying breaths, reminds Philippe that Louis is his brother. Philippe's mask is removed so that D'Artagnan can see his face one last time. Saying the musketeer call, D'Artagnan dies as Philippe comments that D'Artagnan was the one wearing the mask all along. Closing his eyes, Philippe embraces his father one time only as he starts to mourn over his death. D'Artagnan's right-hand man, Lieutenant Andre, is furious at Louis for killing D'Artagnan and upon finding out Philippe was brother to Louis and of royal blood, orders his men to close the door and swears them to secrecy. By the time another battalion breaks in, the three Musketeers and Lieutenant Andre have made Louis and Philippe swap clothes and locked Louis in the iron mask. Philippe introduces Athos, Porthos, and Aramis as his royal council and truest friends. Posing as the king, Philippe orders the guards to take Louis and lock him away. The Musketeers give their respect and kneel before Philippe, honoring him as their true King.Philippe, Athos, Porthos, Aramis, and Queen Anne attend D'Artagnan's funeral, in which The Three Musketeers are finally redeemed. After the funeral, Philippe asks Athos to love him like a son and Athos accepts, kissing Philippe's hand. Afterwards, The Three Musketeers walk away through the long line of proud saluting musketeers under the helm of Lieutenant Andre as new captain, while the elite group chants their battle cry "One for All, All for One". Louis (whom Philippe granted royal pardon being his brother) now lives in a country house, where he is often visited by his mother. Thereafter, France was reformed under Philippe (under the alias of Louis XIV) who gave his people food, prosperity, and peace. He is remembered as the greatest ruler in the history of his nation.

Question: Who finds out they are really brothers?
Answer: Philippe and Louis