In the Season 2 recap of Episode 12 (above), Henry told the youngest Jenner that he sees "a situation with an individual from the past" with whom Jenner has been romantically involved. Neither Henry nor Jenner ever mentioned the individual by name, but Jenner's most recent on-again, off-again relationship was with rapper Tyga.
"You want to really set healthy boundaries and say, 'No, no, you can't kind of dip your toes in and leave when you want and can't really commit,'" Henry said to Jenner.
"I think I know who you're talking about," Jenner responded.
Henry also said that even though the situation might be platonic at the moment, it's still "an unhealthy reminder" for Jenner to have the unnamed individual's presence in her life.