Hello,
I’m sorry about the delay here…the related events are based on the tags and event categories and will list the next 3 upcoming events with the same tags/categories as the event whose page you are on. Since every instance of a recurring event will have the same tags/categories, if the next 3 upcoming events are instances of that series, then those are the events that will be displayed as related events by default. You can make changes via a customization – this post might be helpful as a starting point.
We are limited in the amount of support that we can provide for customizations, but if you get stuck or have any questions, please let me know – I’ll be happy to try to point you in the right direction!
Thanks,
Jennifer