Could you please help me to rewrite this sentence.
Since the death of an actor X. Y has elapsed ten years.
I want to use the relative clause.
An actor X. Y., of whom death has elapsed ten years.(I suppose that this sentence is wrong.)
Thank you for your help.
First of all, the first sentence needs rewriting because your verb (has elapsed) does not correspond to the subject (ten years). Also, "an actor X.Y." feels strange: an actor indicates you don't know which one it was, but then you know their name and when they died. So let's write that sentence as:
Since the death of actor X, ten years have elapsed. He is remembered fondly.
"I want to use the relative clause." OK, but you cannot stuff those ten years in a relative clause about actor X like you tried to! You can convey the same meaning as your original sentence as follows:
Actor X, since whose death have elapsed ten years, is remembered fondly.
However, a shorter, more to-the-point version that I feel flows a bit more naturally, would be:
Actor X, who died ten years ago, is remembered fondly.
"of whom death has elapsed ten years" => here, you try to make death the subject of elapse, but it is not. It is the years that have elapsed, not the death! I guess this is the reason as well why you wrote has instead of have in your original sentence.