How do I pick a random object from a Family to instance?

I am building a very basic ball physics game and have grouped various ball types together in a family. What I would like to do is at random intervals replace the family member currently on stage with a randomly selected member.

I had a look into arrays but they just store strings or integers, not object references. However surely a family could be seen as another type of array, are the members given indexes that I can call against?

OT is it possible to speed up the physics simulation over time to increase the games difficulty?

Got it, was going about things in the wrong way, I basically took all my members out of the family and setup individual animation frames on the ball, then at random intervals I can change the animation frame for a different one. Dead easy.