CBSubs: Automatic discount if user has multiple subscriptions possible?

Sorry for the late reply - project has been on hold, but just to explain a bit more about family members: The subscription is not so much for accessing the website, but for a membership to a local sports club. Often we have 2 or 3 members from one family, and we want to give those members a family discount.

I'm thinking of a single login (Joomla user), with multiple subscriptions. Each subscription should contain a record of the individual with name, phone etc. From what I understand now, CB Subs doesn't support custom fields on the subscription.

You could request the additional information regarding extra family members as part of the registration process. You can then use CBSubs Promotions to increase or decrease the price of a plan based off that information.

From what I understand now, CB Subs doesn't support custom fields on the subscription.

Correct.