Floyd Mayweather Balls Out In Mexico For Sister's Wedding

Well, now we know why Floyd Mayweather took his private jet to Mexico ... his sister got married this weekend in Cabo!

Floyd -- along with several TMT staffers and bodyguards -- hit up the Paradisus Los Cabos resort to watch his sister, Deltricia Tawanna Howard, trade "I Dos" with her boyfriend George Forte III.

The ceremony was super romantic -- it all went down on the beach in front of the crashing waves. Floyd rocked a pretty slick white suit.

The rest of the weekend was lit, too ... parties, dancing, ATV excursions and a fireworks celebration when the bride and groom tied the knot!