First Drink of Wine in 22 years… L’CHAIM!
None of the brothers, including Yosef, drank any wine from the time he was sold into slavery. This is because wine makes people happy and they all vowed not to rejoice until they were reunited.
Standing in the palace Yosef was the only brother who realized that they were indeed reunited. That is why he drank the wine. And the brothers? They had no choice but to drink the wine, since Yosef the powerful viceroy, told them to drink.