The idea has only been science fiction so far. However, that may change in the future.
The reproduction of things learned after birth is not likely anytime soon, so an almost identical human genetic clone might be far off. Recent information that Barbra Streisand has had one of her dogs successfully cloned twice, has sparked some conversation, according to The New York Timesin "Barbra Streisand Cloned Her Dog. For $50,000 You Can Clone Yours."
It is likely that some scientist somewhere will set aside ethical concerns and figure out how to clone humans. That could have a profound impact on estate planning. There is currently no legal status for clones.
Someday, the laws of intestate succession may need to determine whether clones have an equal or greater or lesser priority than children. It also might make a difference when and by whom the clone was made.
Reference: New York Times (Feb. 28, 2018) "Barbra Streisand Cloned Her Dog. For $50,000 You Can Clone Yours."