This is wrapper-style delegation, in some contexts also known as a "decorator" or other jargon depending on what you're doing with it.

It's a perfectly legitimate design choice, although i don't know enough about your problem space to know whether it would be more or less appropriate than regular inheritance in this case.

If what you're building really has a traditional inheritance relationship at its core, you might want to use ISA/SUPER for compatibility with standard idiom; if you're dynamically reassigning relationships or stacking multiple behaviors together on the fly, delegation is probably more appropriate. Ask yourself: What's the design challenge driving you to separate this code into two objects/classes? Which parts of it do you think will change most often, and how?