Another way to look at this is the Manhattan GMAT
technique. For a restriction problem like this you want to look at it in two parts:
Total Possible Combos - Restricted Combos.
So total possible without any restrictions is:
8!/(3!)(5!) = 56 total possibilities
Now you look at the restrictions. What is the restriction -- a couple can't be together. How many are restricted? When looking at a restriction it is best to look at them as a total unit. So 1 couple is a unit. We have four couples. How can we arrange this 4 units? 4*3*2*1 = 24 combos restricted.
So 56 - 24 = 32. Your answer.