Sorry to hear about that. I had two male guppies and 3 female guppies. Both male guppies were harrasing 1 of my female swordtails so i removed them from the main tank into a smaller tank. the dominant guppy died shortly thereafter so I decided to move the other male back into the main tank. You cant pick it, sometimes the males will want to breed like crazy and sometimes they wont even look at the females, you're best bet is to buy 1 male and two females from 2 different stores ie a total of two males and four females. That way the females dont get two harrased and get stressed out and die, also have a lot of good hiding areas, maybe get non-flat rocks and lie them on top of each other to form little caves. When a fish is getting stressed out from being harrassed if it doesnt have anywhere to hide it seems to get more harrassed and then eventually die!
Hope ive been of some help