(a)      In construing all provisions of the estates of decedents law and, unless a contrary intention is indicated, in construing the terms of a will, issue means every living lineal descendant except a lineal descendant of a living lineal descendant.

      (b)      A person who is treated as a child of a person pursuant to §§ 1-205 through 1-208 shall be considered for all purposes as:

            (1)      A lineal descendant of the person; and

            (2)      Subject to the exception in the first sentence of this section, a lineal descendant of all persons of whom the person is a lineal descendant.