By Staff Writer (media@latinospost.com) | First Posted: Aug 14, 2014 07:02 AM EDT

Last week, we spoke about Kate Burton appearing on Season 11 of "Grey's Anatomy" to play Ellis Grey, Meredith Grey's mother. Now, Meredith's half sister will also be appearing on the show, affirming what producer Shonda Rhimes described as a "Meredith-centric season."

Recently, actress Ellen Pompeo, who plays the series' title character, posted a snap of her and her "sister from another Mister" on Instagram, reminding fans of the fact that the upcoming season will indeed feature more of Margaret Pierce, Meredith's half sibling, who is played by Kelly McCreary.

"Hopefully, Margaret is going to represent for her a chance to have someone else she can grow close to in the wake of Cristina's departure from Seattle," CarterMatt.com mused.

Meanwhile, McCreary retweeted Pompeo's photo, calling it their "first family photo," according to Wetpaint.

"Ellen's character, Meredith Grey, was seemingly unaware of the DNA she shares with the new Grey Sloan Memorial surgeon when Season 10 left off," the site explained. "She only knew Maggie as Cristina's pick for the hospital's new head of cardio."

"But we fully expect Mer to be clued in when Season 11 premieres in September - especially now that Richard (James Pickens Jr.) knows that he and Mer's mom, Ellis (Kate Burton), had a love child who happens to be his new colleague," the news source added.

The addition of Meredith's half-sister to Season 11's storyline is not something that Rhimes cooked up over the past few months. In fact, the plot has apparently been simmering "since the beginning."

"That was one of the original pieces of story since the beginning with the Richard-Ellis dynamic, but it's been a piece of story since Season 4 when we talked about introducing her," Rhimes told TV Guide. "We were going, 'When's the right time?!' and we were holding it forever. I kept going, 'Not this season, it's not right.' After a while, I was like, 'We're never going to introduce it. The show is going to end without it.'"

"It's going to be interesting to see how it plays out. Because we've all known about it for so long, it's always been layered it," the producer went on. "It's not a thing where we're going in and backdating. It's literally always been layered into the story line. We can literally go back and pull out moments of the show and I'm excited to do so, and point out where it was talked about. It's not going to be so hard to do."

Watch out for "Grey's Anatomy" season premiere on September 25 on ABC.