You have to join. I have no plans of making separated routes for them.
There are 3 possible routes you may take:
* Skip their content. If you don't want to see any lesbian content or even know it exists.
* Join them, but not watch their scenes.
* Join them, and watch their scenes.
As I know that it is an issue for some people, I assure you mc won't be a meat dildo, or third wheel, or anything like that.