Amy Brenneman Amy Brenneman

Reign is keeping it all in the family.

The CW period drama has cast former Private Practice star Amy Brenneman to play Mary's mother, it was announced Monday.

"Yep, it's true. Off to a wardrobe fitting to play the bada--, Marie de Guise, on [Reign]. Watch out, Adelaide Kane, mama's coming," Brenneman, who is married to series executive producer Brad Silberling, tweeted on Monday. Mary's mother was the second wife of King James V and the Queen of Scotland from 1538 to 1542. Her daughter succeeded her after King James' death, which was also just six days after Mary's birth.

Surprising celebrity family ties

After her long-running turns on Judging Amy and most recently Private Practice, Brenneman will next co-star in Damon Lindelof's upcoming HBO series, The Leftovers, based on Tom Perrotta's novel of the same name.

Reign airs Thursdays at 9/8c on The CW. Are you excited to see Brenneman in period costume?

(Full Disclosure: is owned by CBS, one of The CW's parent companies.)