I don't think I've seen much yaoi anime where the guys' privates are shown...
Come to think of it, the only one I know of is Sensitive Pornograph. 😐

So if someone can enlighten me with some titles, it'll be very helpful. 😃

The only one I can think of besides Sensitive Pornograph is a Bara Yaoi called Legend of the Blue Wolves.. But let me warn you, it's not like those flowery sweet yaoi animes you may have seen. There is rape and abuse by a sadistic fat guy. XD If you can stomach that, then by all means!