Neighbors believed he was possibly a billionaire and a member of the famed Rothschild family, the banking dynasty that rose to prominence in 18th century Europe.
But in the days after he died in a house fire at the age of 87, no evidence has been found linking the longtime Hollywood Hills resident to the Rothschild family. It turns out, he wasn't born with the Rothschild surname.
In 1985, William Kauffman changed his name to William de Rothschild, the Los Angeles Times reported.
ABC7 reached out de Rothschild's brother Richard Kauffman, who had no idea his brother was even alive.
"I thought he had passed away 40 years ago. Last contact I had with him was a telephone call. It was kind of odd. It seemed like he had something to tell me," Kauffman said. "He didn't, and when I never heard from him again I kind of presumed that maybe he had an illness, didn't want to talk about it, and just quietly passed away."
De Rothschild had been quietly living in Laurel Canyon - somehow living like a billionaire, with multiple properties and dozens of luxury vehicles on elevators in his garage.
Neighbors and family didn't know where de Rothschild's money came from or who he really was.
"I don't know how he made his money," Kauffman said.
"I was trying to decide whether I should be sad about this, but in reality, I am somewhat happy about it -- that he had a life, even though it might've been somewhat bizarre," Kauffman added. "That he lived a long life, did not pass away in his 40s."
One neighbor described de Rothschild as a kind, gentle soul.
"As far as he goes, there's no deception on his part, absolutely not," the neighbor said. "He was nice to everyone. He never had a bad word to say about anyone, and he was a good neighbor. I considered him a good friend and I'm really sorry that he's gone."
De Rothschild was not posing as a member of the famous family and never said that he was, neighbors said. Yet, his lifestyle and the name could have led people to use their imagination.