Can you share a name with your confirmation patron saint?

My son was asking me this question and I'm actually not sure of the answer so I figured I'd ask here for him. In all the years I've taught confirmation nobody's tried using their same name, but if you're named after a saint, my assumption is that that saint is already your Christian name - in Baptism, therefore you'd be doubling up. Now, I'd imagine there's no rule on this, if there is, it probably short circuits the question, but if there isn't, what are the pros and cons of choosing your own name as a confirmation patron?