And then there were three?
There's a rumor going around the interwebs that Supernatural is going to introduce another character that is Sam and Dean's half-brother by way of John. Yes, there may be a third Summers Winchester brother. It's totally Gambit. The majority of people seem to be freaking out and I believe there has been at least one claim of jumping the start. If this turns out to be true and not a rumor, I actually think it might be a GOOD thing.
First of all, this is not a new concept. Didn't a lot of people think that John was Jo's dad back in season 2? I know I did. And even though John was obviously extremely in love with Mary until the day he died, it would be foolish to think the man never had sex, let alone a variety of drunken trysts where protection was the last thing on their minds. Random children popping up is hardly out of the question.
But the thing is, even if a guy does show up claiming to be John's son, there's no way that Sam and Dean are going to believe him. However, I do think it will bring them closer together. The boys never trust or rely on each other more than when they're defending their family unit against outsiders and anyone saying that they're trying to make their twosome into a threesome will be an automatic threat that the boys would rally against. If they go so far as a paternity test and it is proved positive, that doesn't mean they're going to embrace their newfound brother, though I think they'll have different reasons. Sam would feel betrayed by John again, thinking about how he wasn't there throughout their childhood because he was off impregnating women and will probably look at the new kid's relatively normal life with envy. Dean won't see him as his brother because he is not Mary's son. He is not the child that Dean pulled out of the fire, he is not the little boy Dean has taken care of all his life, and he certainly hasn't been around long enough for Dean to trust him the way he trusts his family.
They did a story like this in X-men (hence my Summers references above) where Cyclops' father had another child after he lost his wife. There was wild speculation for a while until they introduced Gabriel...who turned out to be a complete PSYCHOPATH and killed his father and attempted to kill both his brothers. I think Kripke should take the same route; we have plenty of allies, even though some are gray. We need more antagonists, adversaries that show up repeatedly for the boys to take on, someone that isn't Lilith because that would get old quickly. While Gordon and Henricksen weren't necessarily the most popular characters and people didn't like them as people, a lot thought they were great as characters, devices to be used against the boys, someone whose ass the boys could kick.
What better to strengthen the Winchester bond then to forcibly make sure that no one else can come in? By facing a new brother who isn't with them and isn't really a Winchester, all the better for Sam and Dean to rediscover why they are special, why the love each other, why it's just the two of them.
C'mon, did you really think Sam and Dean were just going to be like, "Oh, you say that you came from our dad's sperm too? Welcome to the family! You get to drive the Impala on Tuesdays and Thursdays."?
I trust Kripke and if this isn't just a rumor, I'm sure he'll make it worth it.
Note: I am currently experiencing just about the worst migraine of my life and am this close to going to the hospital, so if this makes no sense, that's why.