A sole heir is a person who stands to inherit the entirety of an estate upon the execution of another's will, or by operation of the rules of intestacy
Both forms are commonly used. Black's Law Dictionary uses heir at law.
I was considered 'an heir' of my grandmother's estate under the state laws of intestacy.
te the tuy ey yo deje
An heir is someone that inherits from an estate due to being a descendant or relative of the deceased.