Maureen McCormick and Ryan Lochte Join 'Dancing with the Stars'

Ryan Lochte is set to appear on "Dancing with the Stars." (Reuters)

"Dancing with the Stars'" upcoming season is shaping up to be one of its most star-studded yet.

"Brady Bunch" actress Maureen McCormick, Olympic swimmer Ryan Lochte, and singer-songwriter Kenneth "Babyface" Edmonds will all be competing for the coveted mirror ball trophy next season, a source tells ET. 7th Heaven star Beverley Mitchell is reportedly still in talks to join the competition.

Derek and Julianne Hough will also be returning to DWTS next season, another source confirms to ET. Derek will be back as a pro, and Julianne will once again serve as a judge.

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More DWTS season 23 contestants ET previously confirmed include Little Women star Terra Jole, model Amber Rose, "Wizards of Waverly Place" actor Jake T. Austin, and "General Hospital" actress Emma Samms. Popular pro Maksim Chmerkovskiy will also return next season after last appearing in 2014 -- when he won the season 18 trophy with his partner, Olympic ice dancer Meryl Davis.

As for McCormick, DWTS' Instagram account posted a hint on Thursday about who pro Artem Chigvintsev's partner is this season, and judging by the clues, all signs point to the 60-year-old actress.

"Hint: @theartemc's partner is a published author, released a country album, and started acting when she was 9! Who is she? #DWTS," the caption read, which appeared alongside a snap of 34-year-old Chigvintsev.

McCormick released her memoir, "Here's the Story: Surviving Marcia Brady and Finding My True Voice," in 2009, and released a country album in 1995 titled, "When You Get a Little Lonely." McCormick also made her acting debut in "The Farmer's Daughter" in 1965, when she was just 9 years old.

As for Mitchell, ET chatted with former DWTS contestant Jodie Sweetin at the premiere of Kubo and the Two Strings earlier this month, when she revealed that she's definitely talked to the 35-year-old former WB star -- as well as 37-year-old Step by Step actress Christine Lakin -- about appearing on the hit ABC show. Mitchell is filming "Hollywood Darlings" with Sweetin and Lakin -- an unscripted docu-comedy series on Pop -- debuting in 2017.

"We'll see. They might. You never know," Sweetin said.

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ABC doesn't comment on casting speculation. The full cast will be revealed on Aug. 30, on "Good Morning America." The new season of DWTS premieres Monday, Sept. 12, at 8 p.m. ET/PT on ABC.

One pro dancer that we'll definitely miss is Kym Johnson, who told ET exclusively on Monday that she's done with DWTS after marrying her season 20 partner, "Shark Tank" businessman Robert Herjavec, last month.

"I love the show and I'd love to still be part of it but, you know, I still want to hang up my dance shoes and what a way to end," Johnson said when we caught up with the newlyweds at the Television Academy's Performers Peer Group Celebration in Los Angeles.