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!