his family are eating dinner意思是：他们一家正在吃晚饭 his family is happy意思是：他的家庭很快乐.
family作主语时,如果作为一个整体看待,谓语动词用单数形式,如果就其中一个个成员而言,谓语动词用复数形式.嘿嘿