That could be single kitten syndrome.

Basically, a kitten needs to learn from other cats' bites and scratches to know how that feels and stop doing that to others. If a kitten grows up in a house with no other cats, it will never learn not to bite and scratch since human don't bite and scratch back. Currently, if you go to a shelter, usually they will not let you adopt a kitten younger than 6 months if you don't have other cats at home. You need to adopt 2 at a time if one or both are kittens.

My cat Parmie, who has been the single cat all her live, has the similar problem. She bites a lot but not very hard. And we are all under her magic spell completely, we just accept it without complaining.