He reportedly lost his life on Christmas Day after being struck by a car the Sunday before.
Von Anhalt had been knocked unconscious and remained in a coma for a week, reports TMZ.
It is unknown if he was ever aware of the tragic news of his adoptive mum’s passing.
But his father reportedly knew nothing of his accident until the coroner contacted him on Boxing Day.
He told the showbiz news site he thought his adopted son was away in Germany.
Rest In Peace? Nein!! Live the Afterlife in the fullest, like you did before.
“We had some good times and experienced a lot together — memories are the most precious!!
“Prince Oliver of Anhalt, My brother!!! You will stay forever in my heart. I can’t understand the world!!! Why???”
Von Anhalt, a well-known socialite in LA, was one of several adult men who bought their royal titles from Gabor’s husband through adoption.
Von Anhalt acknowledged making millions of dollars by passing the family title to at least 10 other people.
“If someone offers you $2 million, you do it,” von Anhalt reportedly said.
The legendary Hungarian actress suffered a heart attack and passed away after years of health troubles, just two months shy of her 100th birthday.
Von Anhalt had moved to the US 20 years ago and was living in Beverly Hills.
His mansion is currently on the market for $US4.795 million.
It’s now been revealed Gabor suffered a cerebrovascular accident (also known as a stroke), and then fell into a coma where she went into cardiopulmonary arrest.
Her publicist has confirmed she passed away at her Bel Air mansion after spending the last five years on life support.
She is survived by husband, while her only natural child, daughter Francesca Hilton, to second husband Conrad Hilton, died in January 2015.