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. A person who is treated as a child of a person pursuant to §§ 1–205 through 1–208 of this subtitle shall be considered for all purposes as: A lineal descendant of the person; and Except as provided in subsection (a) of this section, a lineal descendant of all persons of whom the person is a lineal descendant.