The Winchesters find out that angels do not reproduce the same way as humans. Castiel explains that his vessel is not pregnant, his grace is simply splitting to make a new angel. But, even the best laid plans sometimes go awry, especially when Heaven is involved. (Destiel. Sabriel. Asexual reproduction. Mpreg. Better summary and tags inside.)
Supernatural - Rated: M - English - Family/Romance - Chapters: 71 - Words: 138,747 - Reviews: 410 - Favs: 559 - Follows: 432 - Updated: 1/29/2014 - Published: 2/25/2013 - [Dean W., Castiel] [Sam W., Gabriel] - Complete