The 62-year-old reality star confronts Disick, her daughter Kourtney Kardashian's ex-partner, in a preview for Sunday's episode of Keeping Up with the Kardashians following reports he's dating Richie.
"What's going on? Are you dating?" Jenner asks Disick. "Are you dating one person?"
Disick confirms he's dating someone in particular, prompting Jenner to specifically ask about Richie. The 34-year-old club promoter responds by saying Jenner knows "who it is."
"Wait, so how old is she?" Jenner inquires. "Because I really don't know. Is she [my daughter] Kylie [Jenner's] age? 20?"
Disick tells Jenner that Richie, the daughter of singer Lionel Richie, is 19 years old. Jenner then recalls how she was 17 when she started dating her late ex-husband, Robert Kardashian, who was 12 years older.
"You were underage," Disick says. "[Sofia's] not."
"Oh, touché," Jenner responds with a laugh.
Disick and Richie re-sparked romance rumors in September after denying dating reports in May. The couple were openly affectionate in social media posts during a trip to Mexico in October.
"Scott and Sofia seem very happy together," a source told E! News at the time.
Disick split from Kardashian in 2015 after nine years of dating. The pair share three children, 8-year-old son Mason, 5-year-old daughter Penelope and 2-year-old son Reign.