solve

 sudoku

If you find two pairs in a line or box then those cells cannot have any other number.

In this puzzle we find four pairs in Box6 leaving only 3 cells with the same numbers

The '3 in a bed' in Box5 makes the 7 in Row4 force the 7 in Box5 to Row6 and this in turn forces the 7 in Box6 into Row5.

Similarly, the 4 in Row6 means that the 4 in Box5 must be in Row4 therefore the 4 in Box6 must be in Row5.

The existing 4 and 7 in Col8 makes the Two Pair 4,7 in c7r5 and c9r5. Those two cells must be a 4 or a 7.

Now take the 1's in Col8 and 9 which make the 1 for Box6 in c7r4 or c7r6. Regardless of the 1 in Row5, we know that c7r5 has to be a 4 or 7 so cannot be a 1.

The 6 in Col8 and the 6 in Row5 forces the 6 in Box6 into c7r4 and c7r6 making Two Pairs with the 1's.

This leaves only 3 cells in Box6 without possible numbers and with 1,4,6,7,8,and 9 taken they must house 2,3 or 5.

While we haven't actually solved any cells, the Two Pairs have reduced the possibilities for later use in the puzzle.

You should be able to fill in the 8 and 9 in Box9 now.