Unfortunately, I don’t have any answer to this question. It really depends on the context, the persons etc. All I can say is you can just keep talking with the person to the point he/she will bring this subject in the conversation — I know it’s how I prefer it to be done. And if you are really interested in this person, you‘ll have to be patient I guess. Otherwise you can talk about your experience and bring this subject yourself in the discussion — in a subtle way of course. There’s no easy way to talk about — what might be — a touchy topic…