Conan O'Brien is dealing with a profound loss.

The former late-night host's mother, Ruth O'Brien, passed away on December 12 at the age of 92, just three days after his father, Dr. Thomas O'Brien, died at 95. The family reported that their father had been experiencing failing health for some time and also noted that their mother died “peacefully” three days later in Brookline, Massachusetts.

Conan's parents were pioneers in their professions. Ruth was among only four women in her Yale Law School class of 1956, as noted in her obituary. As a real estate attorney, she became the second woman to become a partner at her law firm in 1978, and she retired in 1996 after a 25-year career.

Thomas was a physician, epidemiologist, and Harvard Medical School professor for 30 years, according to the Boston Globe. Throughout his career, he worked hard to tackle the dangers of drug-resistant microbes by leading efforts in the use of databases to help doctors quickly respond to outbreaks. Despite his expertise, Conan—who has children Neve, 21, and Beckett, 19, with wife Liza Powel O'Brien—also spoke about his father beyond his professional achievements.

"Science has said there's no such thing as perpetual motion, but my father was proof that that was wrong," Conan said. "My father was in constant motion. And he was interested in everything—absolutely everything."

Indeed, his father introduced his children to late-night shows and comedy movies, which he enjoyed during his medical school days. Conan remembered, "The loudest I've ever heard anybody laugh was sitting next to him in a theater watching Peter Sellers in a Pink Panther movie."

Conan feels fortunate that Thomas, who he described as having a voracious appetite for ideas and people and the crazy variety and irony of life, will be remembered.  "For the rest of my time on earth I will be hearing from people who want to talk with me about my dad, he explained. I've never met anyone like him, and he happens to be my father. If I met him randomly in a hotel lobby, I'd think, 'Who the hell is this guy? He's the most interesting person I've ever met.'"

Conan has previously shared insights into his upbringing and the lively chaos of a full house.

"There were six kids, two dogs, a cat, my grandmother and a parakeet," he mentioned in a 2017 video, where Ruth was honored with the iRelaunch Pioneering Relauncher Award. "I'm not kidding. That house was madness sometimes, lovely madness, but madness. I don't know how they worked it out, but they worked it out pretty well."

Reflecting on his mom's career, Conan acknowledged the effort she put into becoming a partner at Ropes & Gray after seven years.

"I remember my mother coming home and telling her mother, who lives with us, my grandmother, that she made partner," he recalled. "You can imagine what that was like for a woman who was then practically 90 and had grown up in an era when the Irish were discriminated against in Boston. My grandmother watched her daughter, who went to Vassar and Yale Law School on full scholarships, become a law partner."

Along with Conan, the couple are survived by daughters Kate and Jane, and their sons Justin, Neal, and Luke. They also had nine grandchildren.