Avoiding Duplicate Subscriptions

I have 2 products that I sell. Each of those products comes with a subscription, the exact same subscription for each one.

I have been seeing that if someone purchases one product they get that subscription. Down the road, if they purchase the second product the subscription is added again and now they have a duplicate of the same subscription. Resulting in double charging.

Is there a way to have the system recognize that they already have THAT subscription and not create a dup subscription if they do?