American Shorthair and British Shorthair are both short-haired cat breeds, and theoretically it is unlikely that they will give birth to long-haired cats. However, cats’ genetics are complex, and sometimes mutations occur that cause changes in a cat’s hair type.
If your American Shorthair and British Shorthair mixed breed cat gives birth to a long-haired kitten, then It is possible that one or both parents carry the gene for long hair and that these genes are passed on to the kittens.
In this case, you can determine the type of hair your cat has by observing their behavior and characteristics. Generally speaking, long-haired cats have longer and softer coats than short-haired cats, and they generally require more coat care and grooming.