If you are open to a TVF (Table-Valued Function).
Tired of extracting strings (charindex,left,right,...) I modified a parse function to accept two non-like delimiters. In your case this would be ( and ).
Example
Declare @YourTable table (ID int,SomeCol varchar(max))
Insert Into @YourTable values
(1,'blablablablalbaalala (blibliblobloblo) blalblalala (blululublululu)')
Select A.ID
,B.*
From @YourTable A
Cross Apply [dbo].[udf-Str-Extract](A.SomeCol,'(',')') B
Returns
ID RetSeq RetPos RetVal
1 1 23 blibliblobloblo
1 2 53 blululublululu
The UDF if Interested
CREATE FUNCTION [dbo].[udf-Str-Extract] (@String varchar(max),@Delimiter1 varchar(100),@Delimiter2 varchar(100))
Returns Table
As
Return (
with cte1(N) As (Select 1 From (Values(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) N(N)),
cte2(N) As (Select Top (IsNull(DataLength(@String),0)) Row_Number() over (Order By (Select NULL)) From (Select N=1 From cte1 N1,cte1 N2,cte1 N3,cte1 N4,cte1 N5,cte1 N6) A ),
cte3(N) As (Select 1 Union All Select t.N+DataLength(@Delimiter1) From cte2 t Where Substring(@String,t.N,DataLength(@Delimiter1)) = @Delimiter1),
cte4(N,L) As (Select S.N,IsNull(NullIf(CharIndex(@Delimiter1,@String,s.N),0)-S.N,8000) From cte3 S)
Select RetSeq = Row_Number() over (Order By N)
,RetPos = N
,RetVal = left(RetVal,charindex(@Delimiter2,RetVal)-1)
From (
Select *,RetVal = Substring(@String, N, L)
From cte4
) A
Where charindex(@Delimiter2,RetVal)>1
)
/*
Max Length of String 1MM characters
Declare @String varchar(max) = 'Dear [[FirstName]] [[LastName]], ...'
Select * From [dbo].[udf-Str-Extract] (@String,'[[',']]')
*/