A suitable design pattern

I am facing a design issue, where i have to find a suitable design pattern for my small library, which should be easy to understand by the user of my library.

I have a base class and the derived classes from the base class are A,B and C

The requirements consist of the following:

• the User can create an object of type A
• the User can create an object of type B
• The User can create an object that has the type A and B at the same Time
• The user can create an object of type C
• The User can create an object that has the type C and B at the same Time
• The base class can have the type C as well.

I was thikning about using the decorator design pattern, but it seems like i ened up making it look so complex.

So is there any other better design patterns to work with.