Tanks, I must start by saying that although your kittens look very sweet I am not really much of a kitten person, I prefer older cats so my post will be swayed in that direction.
I was concerned that in your other post you admitted to not knowing who the father is. If this means you own two potential dads congratulations!! However I would find that hard to believe unless they were kept separate.
So I presume your female was allowed out whilst she was calling which is very worrying. Not only would she be likely to pick up infections from an unknown tom, she was also likely to have been mated repeatedly from as many toms as were in the area. Many a female has been seriously injured in this way. It also means that you have no idea what health problems a resulting litter may face.
I am sorry if this is not applicable in your case but I just wanted to make the above points. I get the impression that you are a responsible cat owner which is why I was confused as to the question mark about the Dad.
I hope all your kittens find good homes, personally when I get my next cat it will be from a shelter and they will have to be at least 5 years old and have been in the shelter a while. (I'm just being selfish with that really as it will make me feel good to do this!!)
Ninja, I wish we were closer as I could give your cats a lovely home and they'd be in good company as my (neutered) tom hates other cats too!
Am not against breeding cats but would be against allowing a cat to have more than one litter a year - not fair on cat and is just greed.