If the latest Grey's Anatomy rumor proves true, Meredith's ever-growing family tree could sprout yet another branch. A theory that Mercy West’s Dr. Jackson Avery is the Chief’s super-secret love child via Ellis Grey is gaining some traction as of late.

This twist is based largely on speculation spurred by reports of a casting call for a Young Chief and Young Ellis, who will appear in a flashback, and by the fact that Jackson was cast as bi-racial (as opposed to the show's typical blind casting style).

Does this rumor have any merit? Why not ask the man in question what he knows. Here's what Jesse Williams (Jackson) had to say about it in an interview with Fancast ...

Q: The big rumor making rounds is that Jackson will be revealed as Meredith’s half-brother.

Jesse Williams: I have heard that; I did not know that it had catapulted itself to a rumor. Ellen Pompeo and I have actually talked about this, because it would be really interesting and cool and dramatic. But I’d be very surprised if that happened, only because Meredith would have noticed if her mom was pregnant at some point in her [childhood].

Q: True. But Meredith does have a habit of acquiring relatives she does not get along with.

Jesse Williams: Exactly, exactly, so we’ve got that going for us already. [Laughs] But I don’t know how they would reconcile her never noticing her mom being pregnant. I simply don’t know! It could happen. It absolutely could happen.

Q: You’re also conspicuously absent from the new "Seattle Grace On Call" webisodes. That says to me that Ms. Shonda Rhimes has grander plans to keep you busy.

Jesse Williams: Oh I’ve been busy, I can certainly tell you that. I mean, I’ll find out tomorrow what’s happening next week. I don’t have a ton of information ahead of time, so I’m excited as anybody else to find out what the hell is going to happen next for me.

Q: Jackson also seems to walk around with a sense of entitlement – almost as if he knows he has some sort of “ace” up his sleeve.

Jesse Williams: You’re not the first it’s rubbed in a kind of “entitled” way. I think it’s more of a swagger. We’ve seen so many people [during the hospital merger] fall by the wayside for second-guessing themselves and hesitating. It’s a dog-eat-dog business, and if you hesitate for a minute someone will leap in and take your surgery and get an award for it. If Jackson acts like he doesn’t belong there, that will make him vulnerable. The Mercy Westers are still fish-out-of-water here, trying to find their legs and belong. We’re not on solid ground yet.

Q: Exactly. So the way I figure it, it will eventually boil down to Jackson saving his bacon by pleading, “Don’t fire me… Dad! I’m your long-lost son!”

Jesse Williams: I know! That would be really good. I should just blurt it out in a scene. I’m working tomorrow, so I just might do that and blurt it out!

Q: Rather ironically, it’s sounding like Joss Whedon’s super-secret Cabin in the Woods movie is something you can talk about more.

Jesse Williams: Yeah, that’s another thing that’s sort of semi-top secret. I’m one of the leads in that movie, which I’m very, very excited about. It was tough to hear that it’s going to be delayed so long [until January 2011], but it tested really well and they want to pour more money into it. They’re turning it 3-D, and that’s going to take a lot of time and effort, so they must really believe in it. I’m really proud of it. It’s really different.

Q: Hey, it’s Joss Whedon.

Jesse Williams: I know. Joss Whedon is the man, and [director] Drew [Goddard] is also an amazingly talented and hilarious writer. They were both amazing to work with, because they were so excited the whole time. There is blood, there’s gore, there’s murder, all types of s— happening, and they’re giggling like kids in a candy store. We were shooting that thing for like three-and-a-half months, but they kept it fresh. It was a lot of fun.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.