This is a silly question. It asks one to do something that can't be done.
The sentence
- I must go and look for my brothers.
is Intransitive, but Passive can only apply to a Transitive clause.
The Passive rule promotes the direct object to subject, demotes the old subject to an optional object of by, and adds the auxiliary verb be before the past participle form of the main transitive verb. Like this:
- Marie shot my cousin. == Passive => My cousin was shot (by Marie).
But if the clause isn't transitive, there isn't a direct object to promote, and other noun phrases don't usually work.
- Mary slept all day. but not *All day was slept (by Mary).
Sometimes prepositional objects can be passivized, if the preposition is one that makes a transitive verb out of an intransitive one, like look (at) or listen (to)
- We must look at/listen to that again. == Passive => That must be looked at/listened to again.
But that's rarely the case, so most prepositions after verbs don't mark direct objects. And without a direct object, Passive is impossible.
The real solution is to get a new textbook that actually describes English, instead of something like English.
Best Answer
That's an interesting question. Normally, a switch to the passive voice allows the subject in the active voice to be dropped. In the case of your example, this may give rise to an unwanted inference.
If the original used courted instead of married, you could drop the subject and change the tense of courted to produce
However, doing the same with married to produce
gives the impression that Lucy is no longer married.
This is the case with other verbs of the same type. That is, where using the past perfect looks like applying an adjective.
You have the same phenomena with the word employ. Compare:
The way to get around it is to use the form in the second dictionary example above: got married: