User blog comment:Brad Davenport/Angel creation/@comment-98.243.104.144-20150124001918

I don't think any more angels can be created. In season 4, (I think) Castiel tells Dean that there are only a limited number of angels and that more of his brethren are dying every day. Even though I'm sure the amount of angels is too high for a human to count,  So everytime an angel is killed there is one less and a new angel is not created to replace it. I would think that there could be hybrid offspring, nephelim being created, but the show said there was only that one. Though did they mean she was the only one ever or the only one at that time. I presume that the only way to create one is for a full angel (in a vessel) to have sex with a human and become pregnant. I don't think an angel like Anna, who had no grace, could do that. Though after she regained her grace, it could be possible, but an fallen angel without its grace would probably not create a semi-divine offspring, though they might create one that was more intune with the supernatural than most humans.