(a)      An adopted child shall be treated as a natural child of his adopting parent or parents. On adoption, a child no longer shall be considered a child of either natural parent, except that upon adoption by the spouse of a natural parent, the child shall still be considered the child of that natural parent.

      (b)      A child who has been adopted more than once shall be considered to be a child of the parent or parents who have adopted him most recently and shall cease to be considered a child of his previous parents.