5 times friends fought each other in the UFC

#3 Frank Mir vs Roy Nelson

One of the groomsmen at Frank Mir's wedding was in Nelson's corner for the fight

To be clear, Frank Mir and Roy Nelson weren't exactly chums but both being Las Vegas residents, they trained with each other frequently and had a lot of mutual friends. Both had even faced each other in a BJJ tournament many years before this fight, with Nelson getting the better of Mir.

In UFC fight promotion terms, that's good enough to be called a "friendship".

In the lead-up to the fight, Mir and Nelson were very respectful to each other but they did clarify that they were more acquaintances and occasional training partners than friends. The biggest connection between the two was that one of Frank Mir's groomsmen, James Johnson, was in Roy Nelson's corner for this fight.

Mir beat Nelson handily at UFC 130, besting Big Country in every aspect en route to a unanimous decision win.