Conn said he notified the Clemson coaches of the decision on Sunday.
"I think he's still very interested in Clemson, but he's got a brother (Denzel) who goes to Ole Miss and he's got other schools that he likes as well," Conn said. "He's going to clear his mind and take some other visits."
Clemson and Ole Miss, where Denzel is a redshirt freshman linebacker, are still among Nkemdiche's favorites, as are Alabama, LSU, Florida and Oregon. Speculation that the standout plans to commit to Ole Miss aren't true either, Conn said.
The coach said he expects Nkemdiche to take his time with this decision with a likely decision on National Signing Day, Feb. 6.
"At this point, I think it's a family decision," Conn said. "The family's going to get together and make the best decision for Robert."