THREE PEOPLE EATING TOGETHER SHOULD MAKE A BRACHA
When three or more men over the age of Bar Mitzvah eat a meal together, they should make a bracha together. One of them leads the other two. When ten men eat together, then the name of Hashem is also said as part of the prayer. Most people have a custom that the leader makes a bracha over and drinks a cup of wine, after the Birchas Hamazon. This is not done after the third meal on Shabbos.