Start by copying both columns of both sheets to the 3rd sheet and sort them alphabetically.
Data looks like:
Column C is used for formula:
Cell C2: =IF(A1&B1=A2&B2,1,0)+IF(A2&B2=A3&B3,1,0)
Drag formula down.
Filter data on "bigger then 0" and delete the visible rows.
You can then remove the filter and delete column C.