Hi there!
Glad to say that you are misreading the grammar in this sentence. There are six characters that are considered optional romance choices as well as the ability to explore a sibling relationship with an overbearing brother.
Actually, the description of this Interactive Fiction is in need of a bit of an update (which I will get around to the next time I update the actual work) as there are now seven characters with optional romance routes. The main character's parents will also be taking a slightly bigger role in the story, so you will have the opportunity to explore the whole family dynamic if you so choose, but those relationships remain familial. This story does not portray, reference, nor support incest in any way.
Thanks for your interest in this WIP! Hope you have a lovely day!