新概念3册36课,when the brothers were reunited,这个were reunited是被动语态么?为什么用被动形式?

因为他们是*分开的,不是主观意愿分开的,所以重逢的时候也是被重逢了,而不是自个主动找来的.跟下面这个例句类似：She and her youngest son were finally allowed to be reunited with their family...
她和小儿子终于得到允许和家人团聚.