You can have them spayed or neutered as soon as they weigh 2lbs which is around 8-10 weeks. Earlier is better IMO. Cats can start mating as soon as 4 months.
2-3 Weeks of Age Feeding: Bottle feed formula per manufacturer's instruction every 2 - 3 hours until kittens are full but not bloated- usually kittens will.
Newborn kittens are tiny, and they typically only weigh between 1.8 and 5.3 ounces. Newborn kittens typically fit in the palm of your hand. Stage 2: 1-3 Week.
Average weight: 5.3–8.8 ounces (150–250 grams). By 1 week of age, the kitten should have roughly doubled their birth weight. Physical Development. One-week-old.
Average kitten weight during their first weeks ; Week two. 150–250 ; Week three. 250–350 ; Week four. 350–450 ; Week five. 450–550 ; Week six to nine. 550–850.
Five Weeks: The kittens back teeth should start to come through and they'll be able to munch on solid food. If the kittens are of bottle-feeding age (under 5.