It is not uncommon for three male cats from the same litter to hiss and growl at each other after being neutered. Several factors may contribute to this behavior.
Post-Operative Pain: Neutering is surgery, and discomfort afterward can make cats irritable and more likely to lash out.
Stress: The hospital environment, unfamiliar smells, and the experience of surgery can be very stressful for cats.
Changes in Social Dynamics: Neutering lowers testosterone, which can shift the social hierarchy. Other cats may feel threatened or insecure and may act out to maintain their status.
Hissing and growling are normal forms of communication and do not always mean a fight is imminent. To help your cats adjust, provide a quiet recovery space with food, water, and a clean litter box. Be patient, as recovery and adjustment can take a few weeks. If aggression persists, talk to your veterinarian.