Our family has a reunion every year
family 这里指的是家庭,一个家庭,就是单数
His family are waiting for him
这里指的是,他的家人,家庭成员,肯定不止一个,就是复数
明白了没有?我同样可以理解为Our family has a reunion every year他的每一个家人有团聚故复数 His family are waiting for him 她的家庭有个团聚每一个家人有一个团聚？？你觉得对吗？？家庭团聚 His family are waiting for him 在等他啊，家庭如何等他？？ 肯定是他的家人在等他啊