The Book of Reproduction

The ability, as well as the imperative, to reproduce is the very underpinning of creation. Kaballistic works, as well as the Song of Songs by King Solomon, abound with sexual metaphors, as reproductive unions are the basis for growth and development in the spiritual worlds, every bit as much as in the physical world. I would caution to keep in mind that in the spiritual realms we are not dealing with the identical tools as in the physical worlds. Indeed the Kaballists teach us that the true acts are the ones occuring in the spiritual worlds. Whatever activites we engage here with our physical selves, are but a faint relection of those acts, when transformed into activities that are possible when confined to the world of physicality.
The Bris Kehunas Olam therefore explains that this is why in Berishis (Genesis), the Book of Creation, we find only three Mitzvos (commandments), all of which have a connection to the reproductive act. The first comandment found there is פרו ורבו (Pru U'Rvu), be fruitful and multiply. The second commandment is that of ברית מילה (Bris Milah), circumcision. Finally there is one prohibition found, that of not consuming the גיד הנשה (Gid Hanasheh) the sciatic nerve.
This prohibition came into effect after the struggle between Yaakov and the Angel of Esau. Although Yaakov eventually was victorious, the angel did succeed in hurting his thigh. The thigh is used elsewhere to indicate the sexual organs. As such we can understand that that is where Yaakov was injured. Even if we do not wish to go so far, it is not a stretch to say that as Yaakov was hit near his sexual organ, the angel was attemtping to hurt him in such a manner as to prevent him from having any more children.
Our sages teach us that although the angel only caused minimal injury to Yaakov he did create a long term blemish in his offspring, such that there would be generations in which many would cease to follow the Torah. The fact that our sages make it clear that the injury affected his offspring would certainly support our contention that the intent of the injury was connected to affecting his reproductive capabilities.
Yosef is famous for his resistance to the sexual advances of the wife of Potiphar. His restraint in that case led to his naming his offspring names which reflect two of these fundamental commandments. His primary son was named אפרים (Ephraim). Yosef explained clearly that the reason for this name was that הפרני (Hifrani) that God increased me. Looking at the Hebrew letters you will see clearly that this name comes from the same root word as פרו (Pru) of being fruitful.
His other son was named מנשה (Menasheh). In his name we clearly see an echo of the word הנשה (Hahasheh) in the nerve that was affected by the angel.