My Steele got bred by Flurry, and also had missionary with Flurry's vagina, but it does not appear Flurry got pregnant. Given my Steele's virility, I'd expect Flurry to be pregnant now as well. Can Flurry get pregnant?
He should be able to; I recall B confirming that back when he was still writing him. If you can't knock him up, that's a bug; unlike normal pregnancies, frostwyrm pregnancies are guaranteed (regardless of whether it's you or an NPC getting pregnant).