Kittens and Kitten Troubles

In June, we got a little white calico kitten and named her Winter. We returned her after two days because she wasn't eating or drinking, or using the litter box. In July, we got a black calico fluffy kitten and named her Calli. She was a pretty decent little cat, even though she scratched the kids a bit too much. But, the beginning of this month, she went outside and never came back. So then we decided we better get 2 girl kittens (We want a girl cat to have babies.) We found two in one litter and picked them up about a week and a half ago. The grey one is Twix and the black was Velvet, until Sunday when we realized that the black one is definitely not a girl. He is now Shadow. We didn't want another boy cat, but we are attached. Shadow will stay and not have babies. Twix and Shadow actually have been the best kittens yet. Twix doesn't use her claws on the kids at all. They both prefer to be inside around the kids as opposed to in the garage alone. They are playful and cuddly and the kids of course adore them. We won't let them out alone until they have collars and hopefully they will both stay with us. But now, we have a bigger vet expense as we will want shadow spayed young so he does not become the father of Twix's kittens. Boy is getting used to having other cats around. He seems to tolerate these two fairly well, which is good because we still love Boy. We just wanted to have kittens born around the kids again.