These are a pair of siblings I took care as a cat sitter and found this prefect synchronization.
They are brother and sister and they’re almost always seen together and playing together. Whenever bro comes inside when sis is downstairs, she calls out for him until he comes to find her. It’s cute!
Cat Sitter in Hong Kong Cats Mammy says that whether it’s a sibling thing or not, cats certainly form bonds, and in my experience they are distressed when those bonds are broken. Keep them together if possible !!! Keep them happy!!!!