A male kitten can be neutered at any age, but the earlier he is altered the more likely his recovery will go smoothly. The procedure shouldn’t affect his behaviour or physical development.
How old should my cat be before it’s possible to neuter?
The age of your pet will depend on several factors, including its size and temperament. Generally speaking, cats that are between four months and six years old are mature enough to have their testicles removed for medical reasons. However, you should consult with your veterinarian to determine whether surgery would be advisable given your cat’s health condition as well as its temperament (for example if it has a tendency towards aggression).