Credit: Frederick M. Brown/Getty Images Photo: Kelly McCreary

Just when we thought Grey's Anatomy would end Season 10 without any huge bombshells, we got one sitting on the park bench right outside Grey Sloan Memorial. That's where Richard (James Pickens Jr.) found Dr. Pierce (Kelly McCreary), Cristina's selection for the hospital's newest head of cardiothoracics at the end of the episode airing tonight — Season 10, Episode 24: "Fear (of the Unknown)." Richard thought he was just sitting down next to her for small talk. Incorrect!

Dr. Pierce revealed that she was adopted as a child and that she did some digging about her birth mother — and that her birth mother's name is all over the hospital. That's just about when alarm bells started ringing in our head… even before Dr. Pierce told Richard that name: "Ellis Grey."

Yes, Ellis Grey (Kate Burton), as in the legendary surgeon who birthed and (sorta) raised Meredith (Ellen Pompeo) before succuming to Alzheimer's.

That means that Mer has another half-sister, but her first on her mother's side.

But more importantly, we're left to assume that — considering Richard was Ellis's longtime lover — Pierce is his kid, too. He seems to come to the same realization, as he regards his probably progeny with mouth agape.

What did you think of this twist? Sound off in the comments below!

Grey's Anatomy Season 11 airs this fall.

Dan Clarendon is an assistant editor at Wetpaint Entertainment. Follow him on Twitter and Google+!