The 78-year-old Brokaw has denied the allegations.
Brokaw will be replaced at the graduation by Linda McMahon, who serves on President Donald Trump's cabinet as head of the Small Business Administration.
McMahon is a school donor and previously served on the Catholic university's governing board.
“Singles and couples alike fantasize about having three people in the bedroom. Part of the appeal is the sensual overload — so many different body parts all intertwined. A lot of couples like the idea of a threesome for bringing some spark and excitement back into the bedroom.” ?Vanessa Marin, sex therapist