I thought teams in MB were generally 3 on 3?
Nope, MB teams is usually 2v2.
Say on one team you have player 1 and player 2, and on the opposing team you have player A and player B.
First round, player 1 plays player A, and player 2 plays player B.
In the event that both players on the same team win their matches, that team is the winner.
But in the event that one player on a team wins and the other loses, the remaining players play each other to determine the winner.