Single kitten syndrome occurs when a kitten up to 4 months of age doesn’t get social feedback from siblings. Just like kittens will ideally be socialized to humans during the critical early period, kittens benefit additionally from being around other cats during this time. A single kitten may therefore not learn what behaviors are appropriate or inappropriate. For example, hard biting is not appropriate for play. Bothering others while they are eating or sleeping is not appropriate. This lack of feedback can have lasting effects. Fortunately, there are things you can do to prevent and address the symptomatic behaviors. Check out https://www.lovethesecats.com/preventing-fixing-single-kitten-syndrome/ for more details!