Make an existing prefab into a variant?

I made a mistake, and made 5-6 separate prefabs for UI widgets. Now I want to add some common functionality to all of them (like a background image), so I want to create a new base prefab, and make all 5-6 variants of that one.

Is there a smart way of doing so without having to recreate all of them? Like if this was C# I'd create a base class, make all the old classes inherit from the base class, and they would get all of its functionality.

It can be as simple as making the base prefab an empty game object and variants will add all children & components to the base object, and then I'll have to modify the base to add functionality as needed.

Ideas? Is this possible somehow?

Thanks