ET has learned that Allison died on Wednesday after an extended illness.
Kathryn Dennis is mourning the loss of her mother, Allison Calhoun Dennis.
ET has learned that the Southern Charm star's mother (who was a descendent of seventh U.S. vice president John C. Calhoun) died on Wednesday after an extended illness. She was 59.
"Their family requests privacy while they mourn with the sad loss," a source close to Kathryn told People, which was first to report the news on Thursday. "They're very private people and they want their time to cope."
Kathryn told the outlet in April that she was "incredibly close" to her mom, even referring to her as her "best friend."
"She stuck by me through so much," Kathryn said at the time, adding that her mom had previously battled with cancer. "I don't know what I would do without her."
"She was sick for a year and a half and I was taking care of her," she continued. "She's since been living with me, essentially. It's great to have her around, especially because she's so good with the kids [St. Julien, 3, and Kensie, 5]. She's amazing. She's the best mom I could ever hope for with everything."
In addition to Kathryn, Allison is also survived by her husband, Luke Dennis, and son, Luke Dennis Jr.