Thanks To All For Helping Me. Here is a Code To Get Employee Connected Directly or Indirectly by a Senior.
with CTE as ( select Employee_Id
from Employee
where SeniorId = @Employee_Id
union all
select child.Employee_Id
from Employee child
join CTE parent
on child.SeniorId = parent.Employee_Id
)
Select * from Emplyee Where Employee_Id in (select * from CTE)