How to bring up circumcision with my parents?

Communicate. The question is a puzzle. ?Why was it done or not done? Do you think you want it if it wasn't done? A circ is a simple procedure for newborns but a bit complicated after a month of age. It requires complicated anesthesia, pain management & followup.Do you want it because you are different than your friends?Want it for potential medical reasons?Sort out the issues & be straight with the folks.
Bring up what? To discuss why you were or were not circumcised or because you wish to be circumcised. Screw up your courage and talk to them. You may feel more comfortable discussing it one on one rather than one on two.
Direct approach. I would directly approach them about the pros of circumcision. Hope this helps.