A person who receives an inheritance from a very distant relative is called a "laughing heir!"

In the law of inheritance, a “laughing heir” is a person who gets all of the stuff and none of the pain. He/she is a person who is legally entitled to inherit the property of a deceased person who had no immediate family, because they are distantly related to the deceased. For the same reason, they have no reason to feel sad or mourn the death of that individual. Thus, in theory, they should only feel joy at receiving new stuff. Hence the term “laughing heir.”

Some jurisdictions have a “laughing heir statute,” which eliminates inheritance rights when the remaining relatives become too remote. In this jurisdiction, if no relative falls within the limitations set by the statute, then the property is transferred to the state-which, in that case. Is also kind of a “laughing heir.”

(Source)