Kisame Hoshigaki is often a popular character in these fanfictions. His powerful and somewhat mysterious nature makes him a great focus. Writers can explore more of his backstory, like his time growing up in the Hoshigaki clan and what led him to become a member of the Akatsuki.
Sometimes, an original Hoshigaki clan character created by the fanfiction writer becomes popular. This character might have unique abilities that set them apart from the known Hoshigaki members in the series. For example, a character with the ability to control ice as well as water, which is a new take on the clan's water - based powers.
Another popular character could be an elder of the Hoshigaki clan. Fanfictions can explore their role in guiding the younger members, their knowledge of the clan's secrets, and how they interact with the outside world. They can be a source of wisdom and also a key figure in any clan - related conflicts or events.