There are just some times when a half plus a half doesn't make one whole. Let me use an analogy...
Take a woman - for instance - who gets married several times. First time she's married to a guy who has a penis but no testicles - so she can have sex but he can't fertilize her (so they can't have children) and he needs testosterone hormone therapy and prescription medication to "get it on". So, the marriage is unsatisfying and she get's a divorce.
This time she's really careful about the guys she meets up with and she specifically states in her personal ad that she wants to meet a guy who has testicles. Well, needless to say, this personal ad makes most of the gentlemen readers think she's a complete fucking freak, and in the end only one guys responds. She marries him immediately. Well, it turns out that the man does have testicles, as he had indeed claimed. Only problem? He doesn't have a penis.
Now the woman is furious. She's married to a man who technically has the potential of fertilizing her, but they can't have intercourse because he has no schlong. The woman realizes two things: (1) she needs another divorce, and (2) she needs to be even more specific in her personal ad. So, divorce proceedings over, and feeble-shadow-of-a-man truly and completely out of her life, she proceeds to place yet another personal ad.
This time, she states very clearly, in no uncertain terms, and paying the extra classified advertizing rate for bold, large font, with select all-capitalized print: "Woman, desperate to start a family, seeks MALE WITH BOTH PENIS AND TESTICLES". It takes her an inordinate amount of time to get the only single response she would ever get to a personal ad as preposterous as this one. After inspecting the merchandise (you know the merchandise to which I refer), she immediately marries him.
Well, after getting to know the guy better, it turns out he is a pre-op transvestite and soon after their marriage he starts feeling comfortable and secure enough in a warm environment of loving acceptance that he has it all chopped off. This time, the woman gets divorced and kills herself. Of course, if she'd known at the time of the divorce that she was destined to kill herself, she probably wouldn't even have bothered with the divorce proceedings. But, I guess some people are just really fastidious about getting all their affairs in order before taking that trip to the big soul laundromat in the sky.
OK, so it seems I drifted off my point there for a moment. What I was trying to get at was that the woman just wouldn't be satisfied that she had married two men who were each half complete in the nether regions department. To her, two servings of half the genitals didn't even come remotely close to one serving of whole genitals. So, a half plus a half doesn't make a whole (let's not even get into figuring out what the significance of the third guy is).
Of course, you may argue that there would be those frigid women who would love nothing better than to have a man with no penis. So perhaps that was a lousy analogy to use. Well, it may have been lousy, but you've got to admit - it was amusing. OK, don't admit it, then! If you don't even have the decency to enjoy my sense of humour, at least I'm comforted by knowing that you had to endure reading up until this point. Anyway, where was I? Ah, incomplete genitals - a subject close to my heart...