Cynthia Bailey and Peter Thomas' marriage once again faced drama due to her sister coming in between them, a preview for the Sunday, Jan. 6 episode of The Real Housewives of Atlanta revealed.

Mallorie told the couple she plans to stay with them for a couple of months, something that Thomas is not happy about.

"So you just move into people's houses without asking?" he asked her.

Mallorie tried turning the attention away from herself and pointed out Thomas' mistakes, such as buying a car without telling Cynthia about it.

"That don't have nothing to do with you," he said.

The tension between Mallorie and Thomas comes from the two not being fond of each other in the past. Tensions ran high when Mallorie hid her sister's marriage license on the day of her wedding.

The preview clip also showed Thomas getting mad at his wife, asking Bailey why she didn't tell him about their new house guest earlier. Her sister staying with them was a matter they should have discussed beforehand, he said.

Cynthia, who told her husband that she had only learned the news a few minutes before he had, admitted in an interview segment that it probably wasn't the best idea for her sister to move in and disrupt her relationship with Thomas.

"I think my relationship with my husband works really well when people respect our space," she said. "This was not planned. Mal showed up out of nowhere. I didn't even know Mal was coming."

Issues with family members aren't the only woes the couple is facing in the show's sixth season. In a December interview with Life & Style, they opened up about the struggles they faced when Bailey underwent surgery to get rid of fibroids growing in her uterus. The health crisis prevented Bailey from being intimate with her husband. He confessed he was not only prepared to cheat, but that he would have left her if she didn't get the surgery.

"There is absolutely no way we could have survived another year if things hadn't changed," he said. "Me and my buddies were planning a trip to Venezuela because nobody knows us there."

The fibroids made Bailey so uncomfortable that she had gone about three months without sleeping with her husband, she admitted. If her husband acted on the temptation to have an affair, she added that they would have definitely split up.

However, since the surgery, all is well between the two again

"We're intimate a lot more now and it feels great," Bailey said.

The Real Housewives of Atlanta airs on Bravo Sundays at 8/7c.

Tags: Real Housewives of Atlanta 6