Beautiful, healthy (lacking in hereditary diseases), strong (both mentally and physically), free thinker (also known as non-NPC), latent or developed psychic abilities. Just to name something that are desired attributes for any human being.
Even with healthy, spiritually-inclined and wonderful women, "any hole a goal" and choosing the wrong person among them FOR YOU can be like throwing ice water onto hot oil if the parts don't fit. As can the children from such a union.