The 68-year-old has picked his brother once again for the role after he was first best man at his wedding to Linda Eastman in 1969 as well as in 2002 when he married activist Heather Mills.
His agent confirmed to UK newspaper Daily Express that Mike will be his best man for the third time.
He said: 'Mike is Paul's right-hand man. They go everywhere together. They know what makes each other laugh and share the exact same sense of humour.'
But the former Beatles star isn't worried about his brother being a bad omen after his second marriage resulted in him paying out a