Boolean union of Pairs of Breps

I have two sets of Breps and I want to union the 1st brep from one set from the 1st Brep from the other set and do the corresponding boolean operation on the 2nd, 3rd, 4th etc.  When I connect both sets to the boolean union, it just seems to want to add everything together. 

I am using version 6.00059


Many thanks