Now he says he's starting to remember.
More than a week after being charged with kidnapping his daughter from Boston, the man has admitted using aliases and knowing the newlyweds who went missing in 1985.
His attorney said his client remembers only "bits and pieces" of his life before 1993, but authorities said they have figured out much of the man's past and have deemed him a "person of interest" in the couple's disappearance.
Los Angeles County sheriff's investigators said Monday that Rockefeller's real name is Christian Gerhartsreiter - a German national who has used several aliases since arriving in the United States as a student many years ago.
Homicide detectives confirmed Gerhartsreiter's identity after interviews with people who knew him in California in the 1980s, spokesman Steve Whitmore told The Associated Press.
Investigators have also said a fingerprint on a stockbroker's license application under one of his aliases - Christopher Chichester - matched Rockefeller's prints.
Gerhartsreiter, who is being held in Boston on the kidnapping charge, is also being investigated for the disappearance of Jonathan and Linda Sohus.
Under the Chichester name, he rented a guesthouse at an estate owned by Jonathan Sohus' mother in San Marino, a wealthy enclave about 10 miles (16 kilometers) northeast of Los Angeles, investigators said. Jonathan and Linda Sohus were young newlyweds living with the mother when they vanished in 1985.
Rockefeller's Boston attorney, Stephen Hrones, said Rockefeller told him that he barely knew the Sohuses and that the couple left while he was still in California.
Hrones said he used the Chichester name because "he was aspiring to be an actor out there. He was trying to get into the acting business and he thought it was a more appropriate name.
"There is nothing wrong with using aliases as long as you don't use it to defraud," said the attorney, who said Rockefeller also remembers using the alias Christopher Crowe while he worked on Wall Street.
Hrones said his client still believes his real name is Clark Rockefeller and has no memory of being Christian Gerhartsreiter. His client has also claimed to have few memories before 1993 - the last year authorities have found records for a "Clark Rockefeller."
The district attorney's office and FBI in Boston said Monday they were not ready to declare Rockefeller and Gerhartsreiter were the same person.
At the time of his Aug. 2 arrest in Baltimore, Gerhartsreiter had been living under the Rockefeller name. Police have said he snatched his daughter from a Boston street on July 27 in an elaborately planned kidnapping in which he hired two people to drive them to New York.
In the San Marino case, skeletal remains were unearthed at the Sohus property in 1994 when new owners were putting in a swimming pool. Investigators at the time were unable to identify the bones but believed they belonged to Jonathan Sohus. Investigators have requested a new round of forensic tests.
Two women who were friends with Christopher Chichester in the mid-1980s told the Los Angeles Times they noticed much of the backyard at the Sohus home had been dug up around the time the Sohuses disappeared. Chichester told them there had been plumbing problems.
Los Angeles County sheriff's investigators tried to question Gerhartsreiter in Boston last week, but he declined. No charges have ever been filed in the disappearance case.
The confirmation of the suspect's identity from the Sheriff's Department appears to support an account by Alexander Gerhartsreiter, who said he was the brother of the man being held in Boston.
Found at his home in Bergen, Germany, Alexander Gerhartsreiter told Boston Herald reporters that his brother was the son of an artist and homemaker in Upper Bavaria who felt like he was better than his modest upbringing.
He said his older brother is 47 and was born in Siegsdorf, Germany, then raised until 1978 in the same house where his family lives today.
Alexander Gerhartsreiter said his brother moved to Connecticut as a student and never returned, initially keeping in contact but out of touch since 1985.