As you probably know, Romeo/Mercutio/Benvolio sneaked into their rival party's ball too see a girl. Tybalt notices and decides not to make a commotion or Prince Escalus will kill them. The next day Tybalt sees them, and confronts them. By now Romeo has married Juliet, therefore he is Tybalt's cousin. So, Romeo pleads for the sides not to fight. Since Romeo won't fight Tybalt, Tybalt challenges Mercutio. As the fight is going on, Romeo seperates them, and Tybalt out of nowhere kills Mercutio. Then Romeo kills Tybalt.
Anyway, I dont think anyone in particular started the fight. But the most logical answer would be Tybalt.
If this helped please Mark brainliest!
