They won't stay separate. I am not sure what you mean on their sexes, but if you mean the 2 purebred Swedish are drakes too, meaning 7 drakes to 4 hens, you will almost certainly have fighting as well. I have not had a lot of issues with drakes fighting in my flock, but I always keep a minimum of 1-2 hens per drake (and sometimes like this year, I have some groups with up to 5 hens per drake) and never more than two drakes per pen. If you want to keep 7 drakes together, you will need a *lot* of hens to avoid fighting, probably upwards of 15-20. They are all going to mix and mingle regardless.