Suzane von Richtofen, 22, her former lover Daniel Cravinhos and his older brother Christian are accused of killing Manfred and Marisa von Richtofen as they slept at home in a wealthy district of Sao Paulo in 2002.
Manfred von Richtofen, 49, was an engineer and the great nephew of the World War I German ace known as the Red Baron, police said. His wife was a psychologist.
The couple disapproved of their daughter's relationship with Daniel Cravinhos, who is from a lower-middle class family, the daughter's lawyers have said.
Police said the brothers, who were 21 and 26 when they were arrested four years ago, confessed to the killings, and that Suzane said that she had helped. But the young lovers have had a falling out and now accuse each other of plotting the killings.
Prosecutors said they would seek the maximum sentence of 60 years in prison — 30 for each killing.
The trial originally was to be held June 5, but Suzane von Richtofen's lawyers requested a postponement on grounds that a key witness was out of the country. When Judge Alberto Anderson Filho turned down the request, her lawyers walked out of the courtroom and forced the postponement.
Attorneys for the Cravinhos brothers simply didn't show up for the trial. Judge Anderson Filho has named two lawyers to defend the brothers if their attorneys again fail to appear.
Eleonora Nacif, one of von Richtofen's lawyers, said the missing witness was a close friend of Marisa von Richtofen who was expected to testify that the mother feared that "Suzane was psychologically dependent on Daniel" and that he was manipulating her to get money.
The woman's attorneys have also said that Daniel Cravinhos had threatened to leave her if she didn't get rid of her parents.
Police say that in October 2002, von Richtofen let her lover and his brother into the house at night and checked to make sure her parents were sleeping.
Then, police say, the brothers sneaked into the parents' bedroom and bludgeoned them to death with iron bars.
The house's library was ransacked to make it look like a break-in and Daniel and Suzane went to a motel to fabricate an alibi, police said.
But police say the brothers took some $7,000 from the house, and investigators were led to Christian when he purchased a new motorcycle the day after the murder, paying for it with 36 $100 bills.