Who is the rightful heir of a piece of property left by a deceased person, their parent, spouse or heirs?

It depends on many factors.  I assume the person died without a will.  The suriviving spouse is entitled to all community property, or a portion of the separate property.  If there were children, or grandchildren of a deceased child, then they would be entitled to a portion of the separate property.  If there were no children, then the parent(s) would take a portion of the separate property.