Lifestyle Home Aunt Joanna! Pregnant Gaines Welcomes Sister Mary Kay's 'Beautiful Baby Girl' By Karen Mizoguchi Published on January 4, 2018 07:05 PM Share Tweet Pin Email Joanna Gaines is an aunt again! The pregnant Fixer Upper star, 39, announced her sister Mary Kay McCall and brother-in-law David welcomed their sixth child with a sweet family photo montage on Instagram Thursday. “My sister had her beautiful baby girl! #motherofsix #butshelooks16,” Gaines, 39, captioned the photos. The baby news comes two days after Joanna and husband Chip Gaines, 43, announced they are expecting their fifth child. RELATED GALLERY: Tour Pregnant Joanna Gaines’ ‘All Time Favorite’ Fixer Upper, Designed for Her Sister In another photo, the mother-to-be posed with Mary Kay (who they call Mikey), older sister Teresa Criswell and their mom Nan Stevens. Joanna previously celebrated the birth of Mary Kay’s fifth child on Instagram in February 2015. Fans of Fixer Upper have already been introduced to Mary Kay. On Tuesday night’s episode of the hit HGTV show, Chip and Joanna took on their “all-time favorite” project, making over a home in Waco, Texas, for her younger sister. The same night Mary Kay’s episode aired, the Gaineses surprised fans with the news that Joanna is pregnant. “Gaines party of 7.. (If you’re still confused.. WE ARE PREGNANT) @joannagaines,” Chip wrote along with a photo of the couple cradling his fake baby bump while Joanna shows off hers under a grey sweater. The couple is already parents to children, Drake, 12, Ella, 11, Duke, 9, and Emmie Kay, 7. Fixer Upper airs Tuesdays at 9:00 p.m. EST on HGTV.