Welcome to the Katie and Sadie club.
This might be a little unnecessary, but I wish that this club would not be reported as a duplicate.
You see, this is not a ファン club または either Katie または Sadie, または Katie and Sadie's friendship, like the other two クラブ which can be found when searching similar keywords. This is a club for Katie X Sadie, meaning Katie and Sadie as a couple.
Yuri, slash, lesbians, I don't care what あなた call them, just 登録する if あなた like Katie and Sadie as a couple.

If あなた do not like same-sex couples, または KatieXsadie in general, I suggest that あなた leave. Please do not bash the pairing...