Counting number of children in hierarchical SQL data

ALTER PROCEDURE [dbo].[GetEmployeesstaffwise2] ( @id varchar(30) , @unitid varchar(40))
AS ;
    WITH    EmployeeManager
    AS(
   

SELECT distinct Boss.ID, tbl_Staff.Firstname+' '+tbl_Staff.Middlename+' '+tbl_Staff.Lastname  Employee ,  Boss.Firstname+' '+Boss.Middlename+' '+Boss.Lastname Boss FROM tbl_Staff
 INNER JOIN tbl_Staff AS Boss ON tbl_Staff.mgr=Boss.ID
  INNER JOIN  tbl_Staff BigBoss ON Boss.ID=BigBoss.mgr  or tbl_Staff.mgr=Boss.ID
   where BigBoss.mgr=@id   and Boss.UnitID like'%'+@unitid+'%' and BigBoss.UnitID like'%'+@unitid+'%' and tbl_Staff .UnitID like'%'+@unitid+'%'
 ) select ID,employee as name,Boss as manager from EmployeeManager
















ID ParentID name Children
1 NULL kk 9
2 1 jin 8
3 2 NULL 3
4 2 NULL 2
5 3 NULL 1
6 2 NULL 0
7 3 NULL 0
8 4 NULL 0
9 4 NULL 0
10 5 NULL 0



 ;WITH ChildrenCTE AS (
  SELECT  RootID = ID, ID
  FROM    [treestructure]
  UNION ALL
  SELECT  cte.RootID, d.ID
  FROM    ChildrenCTE cte
          INNER JOIN [treestructure] d ON d.ParentID = cte.ID
)
SELECT  d.ID, d.ParentID, d.name, cnt.Children
FROM    [treestructure] d
        INNER JOIN (
          SELECT  ID = RootID, Children = COUNT(*) - 1
          FROM    ChildrenCTE
          GROUP BY RootID
        ) cnt ON cnt.ID = d.ID