Isn't this verb reciprocal?
passive when used as a transitive verb
Collins labels its use as [be VERB-ed + with].
Longman labels it as: Reunite is usually passive when used as a transitive verb; "be reunited with somebody" (likewise there's an entry for the idiom "be entwined (with something)", for which Wiktionary offers a note "Particularly used in attributive form entwined.")
What is the reason behind using reunite in so-called "passive" even in a sentence where there's no semantic agent and meaning? Secondly, is there a pattern that a group of verb such as reunite follow? --Backinstadiums (talk) 10:48, 24 February 2020 (UTC)