SQL Compare rows of a table with multiple columns

I have a table T1

Id	Col1	Col2	IsActive
1	T1	v1	1
2	T2	v2	0

Now received the following data and it need to be inserted into the above table.

|  Col1  |  Col2  |  
|--------|--------|
|   T1   |   v1   |
|   T2   |   v2   |
|   T3   |   v3   |   

As this data contains some duplicated values, it need to be inserted based on IsActive Column value. For row with IsActive 1, need to insert with IsActive 2 and for row with IsActive 0, need to insert with IsActive 1 like below, the unique data need to be inserted with IsActive 1 and that is not a problem right now

Id	Col1	Col2	IsActive
1	T1	v1	1
2	T2	v2	0
3	T1	v1	2
4	T2	v2	1
5	T3	v3	1

I have created a Temp table #Temp and inserted common rows in new incoming data and data from existing table like below:

#Temp

Col1	Col2	IsActive
T1	v1	1
T2	v2	0
T1	v1	NULL
T2	v2	NULL

Using Group By I can able to select duplicate rows but I need to insert based on IsActive value, so I stuck here.

insert into T1
select Col1, Col2, '1' from #Temp
GROUP BY Col1, Col2
HAVING COUNT(Col1) > 1

I need help on this above part, thanks in advance

Answer

Try this:
    
-- create temp table with values to be inserted
INSERT INTO #ToInsert
    ([Col1], [Col2])
VALUES
    ('T1', 'v1'),
    ('T2', 'v2'),
    ('T3', 'v3')

-- join each value of the temp table to the original table. if
-- value exists increment its `IsActive` by 1, otherwise set it to 1
INSERT INTO t (Col1, Col2, IsActive)
SELECT i.Col1, i.Col2, COALESCE(t.IsActive + 1, 1) AS IsActive
FROM #ToInsert i
LEFT JOIN (
   SELECT Col1, Col2, max(IsActive) as IsActive
   FROM t 
   GROUP BY Col1, Col2
) t ON i.Col1 = t.Col1 AND i.Col2 = t.Col2

Demo here