Two decades ago, the surname Kardashian wasn't synonymous with headline-making reality stars. It was synonymous with Robert Kardashian Sr. — ex-husband of Kris Jenner and father to Kourtney, Kim, Khloé, and Robert Jr. — a businessman and attorney who defended his friend O.J. Simpson during the football star's murder trial. But how did Robert Kardashian become friends with O.J. anyway?

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As HuffPost reports, Robert and O.J. met on a tennis court in 1970 and hit it off right away. O.J. even lived with Robert in Beverly Hills during an off-season from the Buffalo Bills later that decade. The house was "a true bachelor's pad," as friends later told the Los Angeles Times.

Their friendship only grew as Robert married Kris (then named Kris Houghton) in 1978 and as O.J. married Nicole Brown in 1985. The two couples dined out together, hit up nightclubs, and spent Christmases in Aspen.

Robert and O.J. also went into business together. With another investor, they opened a fashion boutique at the University of South California (their mutual alma mater), one of the first frozen yogurt shops in Los Angeles' Westwood Village shopping district, and a corporation called Juice Inc. In the 1980s, Robert and O.J. invested in a business called Concert Cinema, which played music videos in movie theaters before feature films.

Their friendship lasted decades, even though Robert's divorce from Kris in 1991 reportedly distanced him from O.J.'s social circle. At a surprise party for Robert's 50th birthday in February — just four months before the double murder of Nicole Brown and Ron Goldman — O.J. presented him with an autographed jersey. A friend said the party and the jersey meant a lot to Robert. "He loved the lifestyle — the sports, the restaurants, the scene," this friend told the Times.

After O.J. was arrested and charged with murder, Robert joined O.J's "dream team" of defense attorneys, even though he hadn't set foot in a courtroom in 20 years and had little experience with criminal cases. But his role wasn't so much lawyer as it was handler. "I know O.J. better than anyone on the legal team," Kardashian said in an interview, per the Times. "There are so many things I know about his personality. My job is really strategy and liaison between the lawyers and O.J."

And though Robert stuck by his friend's side during the trial, he later expressed "doubts" in a 20/20 interview. "The blood evidence is the biggest thorn in my side; that causes me the greatest problems," he told Barbara Walters in 1996, per The New York Times. "So I — I struggle with the blood evidence."

In 2003, after two more marriages, Robert died of esophageal cancer. After his acquittal in the murder case, O.J. remained a free man until his 2008 conviction on multiple felonies, including kidnapping and robbery. He was released in October 2017 after nine years in prison.