I can't get pictures to post as the kits are wiggly and it takes both of my hands to check, but I decided to give a serious try at sexing our 12-day old bunnies today and it APPEARS that yes, it's possible, at least to a degree.
If I'm correct (and I've come to understand, both through my own mistake and others' that it's very common to be wrong) then I only have 3 bucklings in a litter of 9?? Is that even possible? At least, 3 of them do look like they have a little 'tube' (cheerio) while the others appear to be doelings. It's not critical that I sex them correctly at this age and I will check again on a regular basis, but it's fun to try!!
Ok, I'll admit, the kits aren't THAT wiggly, they're actually being pretty cooperative, but it still takes both hands to expose their little parts. I need another person to snap pictures! lol