Novak Djokovic and Aryna Sabalenka were victorious in Melbourne.
Kelce jumped into Mahomes' postgame interview to declare Arrowhead Stadium "Mahomes' House" after Bengals fans called it 'Burrowhead'.
The Bengals made the most of an out-of-sorts Patrick Mahomes to reach the Super Bowl last year, but a brave display secured revenge.
Brock Purdy was forced off with an elbow injury but the San Francisco 49ers remained confident of a comeback victory against the Eagles.