I think so because guys do not really mind. Or if you feel uncomfortable to ask then just ask indirectly. Perhaps you can ask about intimacy issues. It really depends on how open your relationship is by this time. I mean, in a boy-girl relationship, that topic is discussed sooner or later. It is also good if your partner is open to you about such things. It helps you get to know him or her better. It also gauges your level of understanding and acceptance of his past. I just hope that once you learn about it, it will not elicit doubt and jealousy from you since that's part of his past now. It is behind him now. What's important is the here and now and that is you at present.