How can I help my kittens get along? One is hissing at the other
I brought my female kitten (8 months, spayed) to my parent's house where they have a male kitten (10 months, neutered) and he is perfectly fine and wants to play and shows no signs of aggression towards the newcomer. But she (the newcomer) is hissing at him and is aggressive.
She is fine being at a new house, she likes to explore and go around, she just attacks him. We keep them separated by doggy door. They were both rescued at a few months old (he was found in the woods, and she was adopted from PetSmart but was originally found near an apartment complex where she lived in a cat colony). What can I do to help them get along?