There have been a few posts on this topic in the past. Perhaps you will find some of these interesting:
This first post is about Yin Yoga and the
prostate.
This post is about the perineum and how we can use
bandhas in Yin Yoga to strengthen this area.
You can visit this page for general interest in Yin Yoga and
sexuality.
Generally, strengthening of the pelvic muscles is possible, but I would suggest mostly by using yang forms of exercise. Kegel exercises are great for men and women and are highly recommended! (See the bandha article for info on how to do them if you don't know.) If you still have questions after reading these posts, please let me know.
Cheers
Bernie