We have 2 new kittens, they are siblings, a boy and a girl. Right now they are only 10 weeks old, but I am concerned for the future when they reach sexual maturity. I read they can breed as early as 3 months old, and our vet said she won't alter either of them until they're at least 6 months. We really don't want Luna having kittens of her own, ESPECIALLY since she will be so young if she does. We don't mind finding a new vet for them, we're thinking of changing vets anyways. What would be the youngest/best age to alter them to avoid a litter? I don't care if it's the male or the female first (if one could be altered earlier), we don't have any other unaltered cats to worry about.